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V I S UA L Q U I C K S TA R T G U I D E PHP for the Web Fifth Edition LARRY ULLMAN Peachpit Press Visual QuickStart Guide PHP for the Web, Fifth Edition Larry Ullman Peachpit Press 1301 Sansome Street San Francisco, CA 94111 Find us on the web at: www.peachpit.com To report errors, please send a note to: errata@peachpit.com Peachpit Press is a division of Pearson Education. Copyright © 2016 by Larry Ullman Senior Editor: Karyn Johnson Development Editor: Robyn G. Thomas Copyeditor: Liz Welch Technical Reviewer: Paul Reinheimer Proofreader: Scout Festa Production Coordinator: David Van Ness Compositor: WolfsonDesign Indexer: Valerie Haynes Perry Notice of Rights All rights reserved. No part of this book may be reproduced or transmitted in any form by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. For Information on getting permission for reprints and excerpts, contact permissions@peachpit.com. Notice of Liability The information in this book is distributed on an “As Is” basis, without warranty. While every precaution has been taken in the preparation of the book, neither the author nor Peachpit Press shall have any liability to any person or entity with respect to any loss or damage caused or alleged to be caused directly or indirectly by the instructions contained in this book or by the computer software and hardware products described in it. Trademarks Visual QuickStart Guide is a registered trademark of Peachpit Press, a division of Pearson Education. Macintosh and Mac OS X are registered trademarks of Apple Computer, Inc. Microsoft and Windows are registered trademarks of Microsoft Corp. Other product names used in this book may be trademarks of their own respective owners. Images of websites in this book are copyrighted by the original holders and are used with their kind permission. This book is not officially endorsed by nor affiliated with any of the above companies. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and Peachpit was aware of a trademark claim, the designations appear as requested by the owner of the trademark. All other product names and services identified throughout this book are used in editorial fashion only and for the benefit of such companies with no intention of infringement of the trademark. No such use, or the use of any trade name, is intended to convey Endorsement or other affiliation with this book. ISBN-13: 978-0-134-29125-3 ISBN-10: 0-134-29125-5 9 8 7 6 5 4 3 2 1 Printed and bound in the United States of America Dedication For Jessica, Gina, and Rich, with gratitude for all their love and support. Special Thanks to: Many, many thanks to everyone at Peachpit Press for their assistance and hard work, especially: Robyn Thomas, for managing the project adeptly, and for knowing when to push and poke. Liz Welch, for fine-tuning my prose with her copyediting skills. Paul Reinheimer, for the superlative technical review, keeping me honest, and finding things to improve even in a fifth edition. Scout Festa, for the sharp proofreading eye. David Van Ness, who takes a bunch of disparate stuff and turns it into a book. Thanks for doing what’s required to create, publish, distribute, market, sell, and support these books. My sincerest thanks to the readers of the other editions of this book and my other books. Thanks for your feedback and support and for keeping me in business. Rasmus Lerdorf (who got the PHP ball rolling), the people at PHP.net and Zend.com, those who frequent the various newsgroups and mailing lists, and the greater PHP and open source communities for developing, improving upon, and supporting such wonderfully useful technology. Zoe and Sam, for continuing to be the kid epitome of awesomeness. Jessica, for doing everything you do and everything you can. Table of Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . ix Chapter 1 Getting Started with PHP . . . . . . . . . . . . . . . . . 1 Basic HTML Syntax . . . . . . . . . . . . . . . . . . . . . . 2 Basic PHP Syntax . . . . . . . . . . . . . . . . . . . . . . . 7 Using SFTP . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Testing Your Script . . . . . . . . . . . . . . . . . . . . . . 12 Sending Text to the Browser . . . . . . . . . . . . . . . . 15 Using the PHP Manual . . . . . . . . . . . . . . . . . . . . 18 Sending HTML to the Browser . . . . . . . . . . . . . . . 21 Adding Comments to Scripts . . . . . . . . . . . . . . . . 24 Basic Debugging Steps . . . . . . . . . . . . . . . . . . . 27 Review and Pursue . . . . . . . . . . . . . . . . . . . . . 29 Chapter 2 Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 What Are Variables? . . . . . . . . . . . . . . . . . . . . . 32 Variable Syntax . . . . . . . . . . . . . . . . . . . . . . . 36 Types of Variables . . . . . . . . . . . . . . . . . . . . . . 38 Variable Values . . . . . . . . . . . . . . . . . . . . . . . . 41 Understanding Quotation Marks . . . . . . . . . . . . . 44 Review and Pursue . . . . . . . . . . . . . . . . . . . . . 48 Chapter 3 HTML Forms and PHP . . . . . . . . . . . . . . . . . . . 49 Creating a Simple Form . . . . . . . . . . . . . . . . . . . 50 Choosing a Form Method . . . . . . . . . . . . . . . . . . 54 Receiving Form Data in PHP . . . . . . . . . . . . . . . . 58 Displaying Errors . . . . . . . . . . . . . . . . . . . . . . 63 Error Reporting . . . . . . . . . . . . . . . . . . . . . . . 65 Manually Sending Data to a Page . . . . . . . . . . . . . 68 Review and Pursue . . . . . . . . . . . . . . . . . . . . . .73 Table of Contents v Chapter 4 Using Numbers . . . . . . . . . . . . . . . . . . . . . . . 75 Creating the Form . . . . . . . . . . . . . . . . . . . . . . Performing Arithmetic . . . . . . . . . . . . . . . . . . . . Formatting Numbers . . . . . . . . . . . . . . . . . . . . Understanding Precedence . . . . . . . . . . . . . . . . Incrementing and Decrementing a Number . . . . . . . Review and Pursue . . . . . . . . . . . . . . . . . . . . . Chapter 5 76 79 83 86 88 92 Using Strings . . . . . . . . . . . . . . . . . . . . . . . . . 93 Creating the HTML Form . . . . . . . . . . . . . . . . . . 94 Concatenating Strings . . . . . . . . . . . . . . . . . . . .97 Handling Newlines . . . . . . . . . . . . . . . . . . . . . 101 HTML and PHP . . . . . . . . . . . . . . . . . . . . . . . 104 Encoding and Decoding Strings . . . . . . . . . . . . . 108 Finding Substrings . . . . . . . . . . . . . . . . . . . . . 113 Replacing Parts of a String . . . . . . . . . . . . . . . . . 117 Review and Pursue . . . . . . . . . . . . . . . . . . . . . 120 Chapter 6 Control Structures . . . . . . . . . . . . . . . . . . . . . 121 Creating the HTML Form . . . . . . . . . . . . . . . . . . 122 The if Conditional . . . . . . . . . . . . . . . . . . . . . . 125 Validation Functions . . . . . . . . . . . . . . . . . . . . 128 Using else . . . . . . . . . . . . . . . . . . . . . . . . . . 132 More Operators . . . . . . . . . . . . . . . . . . . . . . . 135 Using elseif . . . . . . . . . . . . . . . . . . . . . . . . . 144 The Switch Conditional . . . . . . . . . . . . . . . . . . . 148 The for Loop . . . . . . . . . . . . . . . . . . . . . . . . . 152 Review and Pursue . . . . . . . . . . . . . . . . . . . . . 157 Chapter 7 Using Arrays . . . . . . . . . . . . . . . . . . . . . . . . 159 What Is an Array? . . . . . . . . . . . . . . . . . . . . . . 160 Creating an Array . . . . . . . . . . . . . . . . . . . . . . 162 Adding Items to an Array . . . . . . . . . . . . . . . . . . 166 Accessing Array Elements . . . . . . . . . . . . . . . . . 170 Creating Multidimensional Arrays . . . . . . . . . . . . . 173 Sorting Arrays . . . . . . . . . . . . . . . . . . . . . . . . 178 Transforming Between Strings and Arrays . . . . . . . . 182 Creating an Array from a Form . . . . . . . . . . . . . . 186 Review and Pursue . . . . . . . . . . . . . . . . . . . . . 191 vi Table of Contents Chapter 8 Creating Web Applications . . . . . . . . . . . . . . . 193 Creating Templates . . . . . . . . . . . . . . . . . . . . . 194 Using External Files . . . . . . . . . . . . . . . . . . . . 201 Using Constants . . . . . . . . . . . . . . . . . . . . . . 207 Working with the Date and Time . . . . . . . . . . . . . . 211 Handling HTML Forms with PHP, Revisited . . . . . . . 214 Making Forms Sticky . . . . . . . . . . . . . . . . . . . .220 Sending Email . . . . . . . . . . . . . . . . . . . . . . . . 228 Output Buffering . . . . . . . . . . . . . . . . . . . . . . 233 Manipulating HTTP Headers . . . . . . . . . . . . . . . 237 Review and Pursue . . . . . . . . . . . . . . . . . . . . . 241 Chapter 9 Cookies and Sessions . . . . . . . . . . . . . . . . . . 243 What Are Cookies? . . . . . . . . . . . . . . . . . . . . . 244 Creating Cookies . . . . . . . . . . . . . . . . . . . . . . 246 Reading from Cookies . . . . . . . . . . . . . . . . . . . 251 Adding Parameters to a Cookie . . . . . . . . . . . . . . 254 Deleting a Cookie . . . . . . . . . . . . . . . . . . . . . . 257 What Are Sessions? . . . . . . . . . . . . . . . . . . . . .260 Creating a Session . . . . . . . . . . . . . . . . . . . . . 261 Accessing Session Variables . . . . . . . . . . . . . . . 264 Deleting a Session . . . . . . . . . . . . . . . . . . . . . 266 Review and Pursue . . . . . . . . . . . . . . . . . . . . . 268 Chapter 10 Creating Functions . . . . . . . . . . . . . . . . . . . . 269 Creating and Using Simple Functions . . . . . . . . . . 270 Creating and Calling Functions That Take Arguments . 276 Setting Default Argument Values . . . . . . . . . . . . . 282 Creating and Using Functions That Return a Value . . . 285 Understanding Variable Scope . . . . . . . . . . . . . .290 Review and Pursue . . . . . . . . . . . . . . . . . . . . .296 Chapter 11 Files and Directories . . . . . . . . . . . . . . . . . . . 297 File Permissions . . . . . . . . . . . . . . . . . . . . . . . 298 Writing to Files . . . . . . . . . . . . . . . . . . . . . . . 303 Locking Files . . . . . . . . . . . . . . . . . . . . . . . . 310 Reading from Files . . . . . . . . . . . . . . . . . . . . . 313 Handling File Uploads . . . . . . . . . . . . . . . . . . . 316 Navigating Directories . . . . . . . . . . . . . . . . . . . 325 Table of Contents vii Creating Directories . . . . . . . . . . . . . . . . . . . . 330 Reading Files Incrementally . . . . . . . . . . . . . . . . 338 Review and Pursue . . . . . . . . . . . . . . . . . . . . . 343 Chapter 12 Intro to Databases . . . . . . . . . . . . . . . . . . . . 345 Introduction to SQL . . . . . . . . . . . . . . . . . . . . . 346 Connecting to MySQL . . . . . . . . . . . . . . . . . . . 348 MySQL Error Handling . . . . . . . . . . . . . . . . . . . 352 Creating a Table . . . . . . . . . . . . . . . . . . . . . . . 355 Inserting Data into a Database . . . . . . . . . . . . . . 360 Securing Query Data . . . . . . . . . . . . . . . . . . . . 366 Retrieving Data from a Database . . . . . . . . . . . . . 371 Deleting Data in a Database . . . . . . . . . . . . . . . . 376 Updating Data in a Database . . . . . . . . . . . . . . . 382 Review and Pursue . . . . . . . . . . . . . . . . . . . . . 388 Chapter 13 Putting It All Together . . . . . . . . . . . . . . . . . 389 Getting Started . . . . . . . . . . . . . . . . . . . . . . .390 Connecting to the Database . . . . . . . . . . . . . . . . 392 Writing the User-Defined Function . . . . . . . . . . . . 393 Creating the Template . . . . . . . . . . . . . . . . . . . 396 Logging In . . . . . . . . . . . . . . . . . . . . . . . . . .400 Logging Out . . . . . . . . . . . . . . . . . . . . . . . . . 404 Adding Quotes . . . . . . . . . . . . . . . . . . . . . . . 405 Listing Quotes . . . . . . . . . . . . . . . . . . . . . . . .409 Editing Quotes . . . . . . . . . . . . . . . . . . . . . . . 412 Deleting Quotes . . . . . . . . . . . . . . . . . . . . . . 418 Creating the Home Page . . . . . . . . . . . . . . . . . . 422 Review and Pursue . . . . . . . . . . . . . . . . . . . . . 426 Appendix A Installation and Configuration . . . . . . . . . . . . 427 Appendix B Resources and Next Steps . . . . . . . . . . . . . . . 449 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459 viii Table of Contents Introduction When I began the first edition of this book in 2000, PHP was a little-known open source project. It was adored by technical people in the know but not yet recognized as the popular choice for web development that it is today. When I taught myself PHP, very little documentation was available on the language—and that was my motivation for writing this book in the first place. Today things are different. The Internet has gone through a boom and a bust and has righted itself. Furthermore, PHP is now the reigning king of dynamic web design tools and has expanded somewhat beyond the realm of just web development. But despite PHP’s popularity and the increase in available documentation, sample code, and examples, a good book discussing the language is still relevant. Although PHP is in the beginnings of its sixth major release, a book such as this—which teaches the language in simple but practical terms— can still be your best guide in learning the information you need to know. This book will teach you PHP, providing both a solid understanding of the fundamentals and a sense of where to look for more advanced information. Although it isn’t a comprehensive programming reference, this book, through demonstrations and real-world examples, provides the knowledge you need to begin building dynamic websites and web applications using PHP. What Is PHP? PHP originally stood for Personal Home Page. It was created in 1994 by Rasmus Lerdorf to track the visitors to his online résumé. As its usefulness and capabilities grew (and as it began to be utilized in more professional situations), PHP came to mean PHP: Hypertext Preprocessor. The definition basically means that PHP handles data before it becomes HTML—which stands for Hypertext Markup Language. According to the official PHP website, found at www.php.net A, PHP is “a popular general-purpose scripting language that is especially suited to web development.” More specifically, PHP is a scripting language commonly embedded within HTML. Let’s examine what this means in more detail. To say that PHP can be embedded into HTML means that PHP code can be written within your HTML code—HTML being the language with which all web pages are built. Therefore, programming with PHP starts off as only slightly more complicated than hand-coding HTML. Also, PHP is a scripting language, as opposed to a compiled language. This means that PHP is designed to do something only after an event occurs—for example, when a user submits a form or goes to a URL (Uniform Resource Locator— the technical term for a web address). Another popular example of a scripting language is JavaScript, which commonly handles events that occur within the browser. Both PHP and JavaScript can also be described as interpreted, because the code must be run through an executable, such as the PHP module or the browser’s JavaScript component. Conversely, compiled languages such as C and C++ can be used to write stand-alone applications that can act independently of any event. A As of this writing, this is the appearance of the official PHP website, located at www.php.net. Naturally, this should be the first place you look to address most of your PHP questions and curiosities. PHP 6? Yes, as of this writing, the current versions of PHP were 5 and 7, but not 6! There’s a long and amusing story here, but the short version is that PHP 6 was actively developed for a while. After hitting many snags, the development was halted and the created work was rolled into PHP 5. When it became time to work on the next major version, after much debate it was decided that that version would be named PHP 7. So although there was once a beta version of PHP 6, no final release ever saw the light of day. x Chapter You should also understand that PHP is a server-side technology. This refers to the fact that everything PHP does occurs on the server (as opposed to on the client, which is the computer being used by the person viewing the website). A server is just a computer set up to provide the pages you see when you go to a web address with your browser. I’ll discuss this process in more detail later in this introduction (see “How PHP Works”). B This Zend website contains useful software as well as a code gallery and well-written tutorials. What PHP Is Not The thing about PHP that confuses most new learners is what PHP can’t do. Although you can use the language for an amazing array of tasks, its main limitation is that PHP cannot be used for clientside features found in some websites. Using a client-side technology like JavaScript, you can create a new browser window, make pop-up dialogs, dynamically generate and alter forms, and much more. None of these tasks can be accomplished using PHP because PHP is server-side, whereas those are client-side issues. But you can use PHP to create JavaScript, just as you can use PHP to create HTML. When it comes time to develop your own PHP projects, remember that you can use PHP only to send information (HTML and such) to the browser. You can’t do anything else within the browser until another request from the server has been made (a form has been submitted or a link has been clicked). Finally, PHP is cross-platform, meaning that it can be used on machines running Unix, Windows, Macintosh, and other operating systems. Again, we’re talking about the server’s operating system, not the client’s. Not only can PHP run on almost any operating system, but, unlike many other programming languages, it enables you to switch your work from one platform to another with few or no modifications. As of this writing, PHP is simultaneously in versions 5.5.35, 5.6.21, and 7.0.6. (There are slight differences between versions 5.5 and 5.6, so 5.5 continues to be supported for a while.) Although I wrote this book using a stable version of PHP 7, all of the code is backward compatible, at least to PHP version 5.x. In a couple of situations where a feature requires a more current version of PHP, or where older versions might have slight variations, a note in a sidebar or a tip will indicate how you can adjust the code accordingly. More information can be found at PHP.net and Zend (www.zend.com), a key company involved with PHP development B. Introduction xi Why Use PHP? Put simply, PHP is better, faster, and easier to learn than the alternatives. All websites must begin with just HTML, and you can create an entire site using a number of static HTML pages. But basic HTML is a limited approach that does not allow for flexibility or dynamic behavior. Visitors accessing HTML-only sites see simple pages with no level of customization or dynamic behavior. With PHP, you can create exciting and original pages based on whatever factors you want to consider. PHP can also interact with databases and files, handle email, and do many other things that HTML alone cannot. Web developers learned a long time ago that HTML alone won’t produce enticing and lasting websites. Toward this end, server-side technologies such as PHP have become the norm. These technologies allow developers to create web applications that are dynamically generated, taking into account whichever elements the programmer desires. Often databasedriven, these advanced sites can be updated and maintained more readily than static HTML pages. When it comes to choosing a server-side technology, the primary alternatives A to PHP are: ASP.NET (Active Server Pages), JSP (JavaServer Pages), Ruby (through the Rails or Sinatra frameworks), and some newer server-side JavaScript options such as Node.js. xii Chapter A The Web Technology Surveys site says that PHP is running on 82 percent of all websites (http://w3techs.com/technologies/overview/ programming_language/all). So the question is, why should a web developer use PHP instead of ASP.NET, Node.js, or whatever else to make a dynamic website? n n HP is much easier to learn and use. P People—perhaps like you—without any formal programming training can write PHP scripts with ease after reading this one book. In comparison, ASP.NET requires an understanding of Visual Basic, C#, or another language; Node.js requires JavaScript. These are more complex languages and are much more difficult to learn. HP was written specifically for P dynamic web page creation. Perl, VBScript, Java, and Ruby were not, and this fact suggests that, by its very intent, PHP can do certain tasks faster and more easily than the alternatives. I’d like to make it clear, however, that although I’m suggesting that PHP is better for certain things—specifically those it was created to do, PHP isn’t a “better” programming language than JavaScript or C#—they can do things PHP can’t. n n HP is both free and cross-platform. P Therefore, you can learn and use PHP on nearly any computer and at no cost. Furthermore, its open source nature means that PHP’s users are driving its development, not some corporate entity. HP is the most popular tool available P for developing dynamic websites. As of this writing, PHP is in use on over 82 percent of all websites A and is the sixth most popular programming language overall B. Many of the biggest websites—Yahoo, Wikipedia, and Facebook, just to name three—and content management tools, such as WordPress, Drupal, Moodle, and Joomla, use PHP. By learning this one language, you’ll provide yourself with either a usable hobby or a lucrative skill. B The Tiobe Index (www.tiobe.com/tiobe_index) uses a combination of factors to rank the popularity of programming languages. Introduction xiii How PHP Works PHP is a server-side language, which means the code you write in PHP resides on a host computer that serves web pages to browsers. When you go to a website (www.LarryUllman.com, for example), your Internet service provider (ISP) directs your request to the server that holds the www.LarryUllman.com information. That server reads the PHP code and processes it according to its scripted directions. In this example, the PHP code tells the server to send the appropriate web page data to your browser in the form of HTML A. In short, PHP creates an HTML page on the fly based on parameters of your choosing. This differs from an HTML-generated site in that when a request is made, the server merely sends the HTML data to the browser—no server-side interpretation occurs B. Hence, to the end user’s Client Script Request HTML PHP URL Request HTML The central difference between using PHP and using straight HTML is that PHP does everything on the server and then sends the appropriate information to the browser. This book covers how to use PHP to send the right data to the browser. Server URL Request HTML Client browser, there may or may not be an obvious difference between what home.html and home.php look like, but how you arrive at that point is critically altered. The major difference is that by using PHP, you can have the server dynamically generate the HTML code. For example, different information could be presented if it’s Monday as opposed to Tuesday or if the user has visited the page before. Dynamic web page creation sets apart the less appealing, static sites from the more interesting, and therefore more visited, interactive ones. Server A This graphic demonstrates (albeit in very simplistic terms) how the process works between a client, the server, and a PHP module (an application added to the server to increase its functionality) to send HTML back to the browser. B Compare this direct relationship of how a server handles basic HTML to A. This is also why HTML pages can be viewed in your browser from your own computer—they don’t need to be “served,” but dynamically generated pages need to be accessed through a server that handles the processing. xiv Chapter What You’ll Need The most important requirement for working with PHP—because it’s a server-side scripting language—is access to a PHPenabled server. Considering PHP’s popularity, your web host most likely has this option available to you on their servers. You’ll need to contact them to see what technology they support. A The popular Dreamweaver application supports PHP development, among other server-side technologies. Your other option is to install PHP and a web server application (like Apache) on your own computer. Users of Windows, Mac OS X, or Linux can easily install and use PHP for no cost. Directions for installing PHP are available in Appendix A, “Installation and Configuration.” If you’re up to the task of using your own PHP-installed server, you can take some consolation in knowing that PHP is available for free from the PHP website (www.php.net) and comes in easy-to-install packages. If you take this approach, and I recommend that you do, then your computer will act as both the client and the server. The second requirement is almost a given: You must have a text editor on your computer. Atom, Notepad++, UltraEdit, and similar freeware applications are all sufficient for your purposes, and TextMate, SublimeText, and other commercial applications offer more features that you may appreciate. If you’re accustomed to using a graphical interface (also referred to as WYSIWYG—What You See Is What You Get) such as Adobe Dreamweaver A or Aptana Studio, you can consult that application’s manual to see how to program within it. continues on next page Introduction xv Third, you need a method of getting the scripts you write to the server. If you’ve installed PHP on your own computer, you can save the scripts to the appropriate directory. However, if you’re using a remote server with a web host, you’ll need an SFTP (Secure File Transfer Protocol) program to send the script to the server. There are plenty of SFTP applications available; for example, in Chapter 1, “Getting Started with PHP,” I use the free FileZilla (http://filezilla-project.org B). B The FileZilla application can be used on many different operating systems to move PHP scripts and other files to a remote server. Finally, if you want to follow the examples in Chapter 12, “Intro to Databases,” you need access to MySQL (www.mysql.com C). MySQL is available in a free version that you can install on your own computer. This book assumes only a basic knowledge of HTML, although the more comfortable you are handling raw HTML code without the aid of a WYSIWYG application such as Dreamweaver, the easier the transition to using PHP will be. Every programmer will eventually turn to an HTML reference at some time or other, regardless of how much you know, so I encourage you to keep a good HTML book by your side. One such introduction to HTML is Elizabeth Castro and Bruce Hyslop’s HTML, XHTML, and CSS: Visual QuickStart Guide (Peachpit Press, 2014). Previous programming experience is certainly not required. However, it may expedite your learning because you’ll quickly see numerous similarities between, for example, Perl and PHP or JavaScript and PHP. xvi Chapter C MySQL’s website (as of this writing). Script i.1 A sample PHP script, with line numbers and bold emphasis on a specific section of code. 1 2 3 4 5 6 7 8 9 10 Hello, World! About This Book This book attempts to convey the fundamentals of programming with PHP while hinting at some of the more advanced features you may want to consider in the future, without going into overwhelming detail. It uses the following conventions to do so. The step-by-step instructions indicate what coding you’re to add to your scripts and where. The specific text you should type is printed in a unique type style to separate it from the main body text. For example: The PHP code is also written as its own complete script and is numbered by line for reference (Script i.1). You shouldn’t insert these line numbers yourself, because doing so will render your work inoperable. I recommend using a text editor that automatically displays the line numbers for you—the numbers will help when you’re debugging your work. In the scripts, you’ll sometimes see particular lines highlighted in bold, in order to draw attention to new or relevant material. What’s New in This Book? I would consider this fifth edition to be a modest revision of an already solid book. The biggest changes are .. All examples now use HTML5. .. The MySQL code uses the most current version of PHP’s MySQL extension. .. We cover PHP 7, as applicable. Finally, I tweaked some of the examples mostly to satisfy my own drive for perfection. No content from the previous edition has been removed. Introduction xvii Because of the nature of how PHP works, you need to understand that there are essentially three views of every script: the PHP code (e.g., Script i.1), the code that’s sent to the browser (primarily HTML), and what the browser displays to the end user. Where appropriate, sections of, or all of, the browser window are revealed, showing the result of the exercise A. Occasionally, you’ll also see an image displaying the HTML source that the browser received B. You can normally access this view by choosing View Source or View Page Source from the appropriate browser menu. To summarize, B displays the HTML the browser receives, and A demonstrates how the browser interprets that HTML. Using PHP, you’ll create the HTML that’s sent to the browser. A This is a sample view you’ll see of the browser window. For the purposes of this book, it won’t make any difference which browser or operating system you use. B By viewing the source code received by the browser, you can see the HTML created by PHP and sent by the server. xviii Chapter Because the columns in this book are narrower than the common text editor screen, sometimes lines of PHP code printed in the steps have to be broken where they would not otherwise break in your editor. A small gray arrow indicates when this kind of break occurs. For example: print "This is going to be a longer ➝ line of code."; You should continue to use one line in your scripts, or else you’ll encounter errors when executing them. (The gray arrow isn’t used in scripts that are numbered.) While demonstrating new features and techniques, I’ll do my best to explain the why’s and how’s of them as I go. Between reading about and using a function, you should clearly comprehend it. Should something remain confusing, though, this book contains a number of references where you can find answers to any questions (see Appendix B, “Resources and Next Steps”). If you’re confused by a particular function or example, your best bet will be to check the online PHP manual or the book’s supporting website (and its user support forum). Introduction xix Companion Website Which Book Is Right for You? While you’re reading this book, you may also find it helpful to visit the PHP for the Web: Visual QuickStart Guide, 5th Edition website, found within www.LarryUllman.com. There you’ll find every script in this book available in a downloadable form. However, I strongly encourage you to type the scripts yourself in order to become more familiar with the structure and syntax of PHP. The site also provides an errata page listing any mistakes made in this text. This is the fifth edition of my first book on PHP. Like the original, it’s written with the beginner or nonprogrammer in mind. If you have little or no programming experience, prefer a gentler pace, or like to learn things in bite-sized pieces, this is the book for you. Make no mistake: This book covers what you need to know to begin developing dynamic websites and uses practical examples, but it does so without any in-depth theory or advanced applications. What many users find most helpful, though, is the book’s supporting forum, found through the website or more directly at www.LarryUllman.com/forums/. Using the forum, you can Conversely, if you pick up new technologies really quickly or already have some experience developing websites, you may find this to be too basic. In that case, you should consider my PHP and MySQL for Dynamic Web Sites: Visual QuickPro Guide instead (Peachpit Press, 2012). It discusses SQL and MySQL in much greater detail and goes through several more complex examples, but it does so at a quick jog. n n n n n n n Find answers to problems you’re having eceive advice on how to approach an R idea you have Get debugging help ee how changes in the technologies S have affected the examples in the book L earn what other people are doing with PHP Confirm the answers to review questions eceive a faster reply from me than if R you send me a direct email xx Chapter How to Ask Questions the Smart Way Whether you’re posting a message to the book’s supporting forum, sending me an email, or asking a question in a newsgroup, knowing how to most effectively ask a question improves the quality of the response you’ll receive as well as the speed with which you’ll get your answer. To receive the best answer in the shortest amount of time, follow these steps: 1. S earch the Internet, read the manuals, and browse any applicable documentation. 2. A sk your question in the most appropriate forum (newsgroup, mailing list, and so on). 3. Use a clear and concise subject. 4. D escribe your problem in detail, show any relevant code, say what went wrong, indicate what version of PHP you’re using, and state what operating system you’re running. Questions, comments, or suggestions? If you have a PHP-specific question, there are newsgroups, mailing lists, and question-and-answer sections available on PHPrelated websites for you to turn to. These are discussed in more detail in Appendix B. Browsing through these references or searching the Internet will almost always provide you with the fastest answer. You can also direct your questions, comments, and suggestions to me. You’ll get the fastest reply using the book’s corresponding forum; I always answer those questions first. If you’d rather email me, you can do so through the contact page on the website. I do try to answer every email I receive, but it will probably take a week or two (whereas you’ll likely get a reply in the forum within a couple of days). For more tips and an enlightening read, see the sidebar on this page and Eric Steven Raymond’s “How to Ask Questions the Smart Way,” at www.catb.org/~esr/faqs/ smart-questions.html. The 10 minutes you spend on it will save you hours in the future. Those people who will answer your questions, like myself, will be most appreciative! Introduction xxi This page intentionally left blank 1 Getting Started with PHP When learning any new programming language, always begin with an understanding of the basic syntax and functionality, which is what you’ll learn in this chapter. The focus here is on the fundamentals of HTML and PHP, and how the two languages work together. The chapter also covers some recommended programming and debugging techniques, the use of which will greatly ease the learning process. If you’ve never programmed before, a focused reading of this chapter will start you on the right track. If you have some programming experience, you’ll be able to breeze through these pages, gaining a perspective for the book’s remaining material. By the end of this chapter you will have successfully written and executed your first PHP scripts and be on your way to developing dynamic web applications. In This Chapter Basic HTML Syntax 2 Basic PHP Syntax 7 Using SFTP 10 Testing Your Script 12 Sending Text to the Browser 15 Using the PHP Manual 18 Sending HTML to the Browser 21 Adding Comments to Scripts 24 Basic Debugging Steps 27 Review and Pursue 29 Basic HTML Syntax All web pages are made using HTML (Hypertext Markup Language). Every web browser, be it Google’s Chrome, Mozilla’s Firefox, Microsoft’s Internet Explorer and Edge, or Apple’s Safari, turns HTML code—

Hello, World!

I just wanted to say Hello. —into the web page presented to the user A. As of this writing, the current version of HTML is 5, which should remain the norm for some time to come (it was officially standardized in 2014). HTML5 is a solid and practical version of the language, well suited for today’s web. Before getting into the syntax of PHP, let’s create one simple but valid HTML document that can act as a template for many of this book’s examples. 2 Chapter 1 A How one web browser renders the HTML code. Basic CSS HTML elements define a page’s content, but formatting the look and behavior of such content is left to CSS (Cascading Style Sheets). As with HTML, this book does not teach CSS in any detail, but because some of the book’s code uses CSS, you should be familiar with its basic syntax. You can add CSS to a web page in a couple of ways. The first, and easiest, method is to use HTML style tags: The CSS rules are defined between the opening and closing style tags. You can also use the link HTML tag to incorporate CSS rules defined in an external file: That file would contain only the rules, without the style tags. CSS rules are applied to combinations of general page elements, CSS classes, and specific items: img { border: 0px; } .error { color: red; } #about { background-color: #ccc; } The first rule applies to every image tag. The second applies to any element that has a class of error:

Error!

The third rule applies only to the specific element that has an id value of about:

About...

(Not all elements need to have an id attribute, but no two elements should have the same id value.) For the most part, this book uses CSS only to do simple things, such as changing the color or background color of an element or some text. For more on CSS, search the web or see a dedicated book on the subject. Getting Started with PHP 3 To create an HTML page: 1. Open your text editor or integrated development environment (IDE). You can use pretty much any application to create HTML and PHP pages. Popular choices include > Adobe’s Dreamweaver (www.adobe.com) B PhpStorm and most other web development applications can create the basics of an HTML document for you. > Aptana Studio (www.aptana.com) > PhpStorm (www.jetbrains.com) > Sublime Text (www.sublimetext.com) > Atom (https://atom.io) The first three are IDEs, making them more complicated to use but also more powerful. The last two are text editors. All these programs run on most common operating systems. 2. Choose File > New to create a new, blank document. Some text editors allow you to start by creating a new document of a certain type—for example, a new HTML file B. If your application has this option, use it! 3. Start with the HTML header lines (Script 1.1): A valid HTML5 document begins with these lines. They tell the web browser what type of document to expect. For this template, and in this entire book, HTML5 pages will be created. One of the niceties of HTML5 is its minimal doctype and syntax. 4 Chapter 1 Script 1.1 This simple document contains the basics of an HTML5 page. 1 2 3 4 5 6 7 8 9 10 11 12 Welcome to this Page!

This is a basic HTML page!

Even with some decoration, it's still not very exciting.

Understanding Encoding Encoding is a huge subject, but what you most need to understand is this: The encoding you use in a file dictates what characters can be represented (and therefore, what written languages you can use). To select an encoding, you must first confirm that your text editor or IDE can save documents using that encoding. Some applications let you set the encoding in the preferences or options area; others set the encoding when you save the file. To indicate the encoding to the browser, there’s a corresponding meta tag: The charset=utf-8 part says that UTF-8 (short for 8-bit Unicode Transformation Format) encoding is being used. Unicode is a way of reliably representing every symbol in every alphabet. Version 8.0.0 of Unicode—the current version as of this writing—supports over 120,000 characters! The most commonly used Unicode encoding is UTF-8. If you want to create a multilingual web page, UTF-8 is the way to go, and it’ll be used in this book’s examples. You don’t have to, of course. But whatever encoding you do use, make sure the encoding indicated by the HTML page matches the actual encoding used by the text editor or IDE. If you don’t, you’ll likely see odd characters when viewing the page in a web browser. 4. Create the head section of the page: Welcome to this Page! ➝ The head of an HTML page should include the charset meta tag. The “Understanding Encoding” sidebar discusses what this means in more detail. The head also contains the page’s title, which appears at the top of the browser window or tab, as well as in the browser’s bookmarks and history. You can also place JavaScript and CSS references in the head. 5. Create the body section:

This is a basic HTML page! ➝

Even with some ➝ decoration, it's still not ➝ very exciting.

The page’s content—what is shown in the browser—goes between opening and closing body tags. 6. Complete the page with a closing HTML tag: continues on next page Getting Started with PHP 5 7. Choose File > Save As. In the dialog box that appears, choose Text Only (or ASCII) for the format, if you’re given the option. HTML and PHP documents are just plain text files (unlike, for example, a Microsoft Word document, which is stored in a proprietary, binary format). You may also need to indicate the encoding (utf-8) when you save the file (again, see the “Understanding Encoding” sidebar). 8. Navigate to the location where you wish to save the script. You can place this script anywhere you’d like on your computer, although using one dedicated folder for every script in this book, perhaps with subfolders for each chapter, makes sense. 9. Save the file as welcome.html. HTML5 pages use the standard .html extension. 10. Test the page by viewing it in your browser C. Unlike with PHP scripts (as you’ll soon discover), you can test HTML pages by opening them directly in a browser. Search the web or use the book’s support forum (www.LarryUllman.com/forums/) to find a good HTML and PHP editor or IDE. For more information on HTML, check out Elizabeth Castro and Bruce Hyslop’s excellent book HTML and CSS, Eighth Edition: Visual QuickStart Guide (Peachpit Press, 2014). 6 Chapter 1 C The HTML page, as interpreted by the browser. Basic PHP Syntax Now that you’ve seen how HTML will be handled in this book, it’s time to begin PHP scripting. To create a PHP page, you’ll start exactly as you would if you were creating an HTML document from scratch. Understanding the reason for this is vitally important: Web browsers are client applications that understand HTML; PHP is a server-side technology that cannot run in the client. To bridge this gap, PHP is used on the server to generate HTML that’s run in a browser (refer to the section “How PHP Works” in this book’s “Introduction” for a visual representation of this relationship). There are three main differences between a standard HTML page and a PHP script. First, PHP scripts should be saved with the .php file extension (for example, index.php). Second, you place PHP code within tags, normally within the context of some HTML: ...

This is HTML.

More HTML

... The PHP tags indicate the parts of the page to be run through the PHP processor on the server. This leads to the third major difference: PHP scripts must be run on a PHP-enabled web server (whereas HTML pages can be viewed on any computer, directly in a browser). This means that PHP scripts must always be run through a URL (for example, http://example.com/ page.php). If you’re viewing a PHP script in a web browser and the address does not begin with http, the PHP script will not work. Getting Started with PHP 7 To make this first PHP script do something without too much programming fuss, you’ll use the phpinfo() function. This function, when called, sends a table of information to the web browser. That table lists the specifics of the PHP installation on that particular server. It’s a great way to test your PHP installation and has a high “bang for your buck” quality. However, the phpinfo() function not only outputs a table of information, it also creates a complete HTML page for you. So this first PHP script does not require the standard HTML code, although subsequent scripts in this chapter will. To create a new PHP script on your computer: 1. Create a new PHP document in your text editor or IDE, to be named phpinfo.php (Script 1.2). For this specific case, you’ll start with a blank file. But if your text editor or IDE has PHP file templates for you, you can certainly start with one of those. 2. Begin the page with 3. Add the following on the next line: phpinfo(); The syntax will be explained in detail later, but in short, this is just a call to an existing PHP function named phpinfo. You must use the opening and closing parentheses, with nothing between them, and the semicolon. 4. Type ?> on its own line, as the last line. The closing PHP tag tells the server that the PHP section of the script is over. Again, because the phpinfo() function generates a complete HTML page for you, no HTML tags are needed. 5. Save the script as phpinfo.php. Not to overstate the point, but remember that PHP scripts must use a valid file extension. Most likely you’ll have no problems if you save your files as filename.php. You also need to be certain that the application or operating system is not adding a hidden extension to the file. Notepad on Windows, for example, attempts to add .txt to uncommon file extensions, which renders the PHP script unusable. (Generally speaking, do not use Notepad.) Just as a file’s extension on your computer tells the operating system in what application to open the file, a web page’s extension tells the server how to process the file: file.php goes through the PHP module, file.aspx is processed as ASP.NET, and file.html is a static HTML document (normally). The extension associations are determined by the web server’s settings. If you’re developing PHP scripts for a hosted website, check with your hosting company to learn which file extensions you can use for PHP documents. In this book you’ll see .php, the most common extension. You’ll occasionally see PHP’s short tags— simply —used in other people’s scripts, although I recommend sticking with the formal tags: . Support for the short tags must be enabled on a server, and using them makes your code less portable. You’ll find it handy to have a copy of the phpinfo.php file around. As you’ll soon see, this script reports upon PHP’s capabilities, settings, and other features of your server. In fact, this book frequently suggests you return to this script for those purposes. PHP scripts can also be executed without a web browser, using a command-line interface and a standalone PHP executable. But that topic is well outside the scope of this book (and it’s a much less common use of PHP regardless). Getting Started with PHP 9 Using SFTP Unlike HTML, which can be tested directly in a browser, PHP scripts need to be run from a PHP-enabled server in order to see the results. Specifically, PHP is run through a web server application, such as Apache (http://httpd.apache.org), Nginx (www.nginx.com), or Internet Information Server (IIS; www.iis.net). You can obtain a PHP-enabled server in one of two ways: n n Install the software on your own computer. Acquire web hosting. PHP is open source software (meaning, in part, that it’s free) and is generally easy to install (with no adverse effect on your computer). If you want to install PHP and a web server on your computer, follow the directions in Appendix A, “Installation and Configuration.” Once you’ve done so, you can skip ahead to the next section of the chapter, where you’ll learn how to test your first PHP script. If you’re not running PHP on your own computer, you’ll need to transfer your PHP scripts to the PHP-enabled server using SFTP (Secure File Transfer Protocol). The web hosting company or server’s administrator will provide you with SFTP access information, which you’ll enter into an SFTP client. Many SFTP client applications are available; this next sequence of steps uses the free FileZilla (http://filezilla-project.org), which runs on many operating systems. To SFTP your script to the server: 1. Open your SFTP application. 2. In the application’s connection window, enter the information provided by your web host A. SFTP access requires a host (for example, the domain name or an IP address), username, and password. 3. Click Quickconnect (or your SFTP client’s equivalent). If you’ve provided the correct information, you should be able to connect. If not, you’ll see error messages at the top of the FileZilla window B. A The connection section of FileZilla’s main window (as it appears on the Mac). B The reported error says that the connection attempt was refused. 10 Chapter 1 4. Navigate to the proper directory for your web pages (for example, www, htdocs, or httpdocs). The SFTP application won’t necessarily drop you off in the appropriate directory. You may need to do some navigation to get to the web document root. The web document root is the directory on the server to which a URL directly points (for example, www.larryullman.com, as opposed to www.larryullman.com/ somedir/). If you’re unsure of what the web document root is for your setup, see the documentation provided by the hosting company (or ask them for support). In FileZilla, the right column represents the files and directories on the server; the left column represents the files and directories on your computer C. Just double-click folders to open them. 5. Upload your script—phpinfo.php—to the server. To do this in FileZilla, drag the file from the left column—your computer—to the right column—the server. Some text editors and IDEs have built-in SFTP capability, allowing you to save your scripts directly to the server. Other applications can run PHP scripts without leaving the application at all. You can also transfer files to your web server using version control software, such as Git (https://git-scm.com). Although this is an excellent route, it’s well beyond the scope of a beginner’s guide to PHP. C I’ve successfully connected to the remote server and navigated into the html directory (aka the web document root). Getting Started with PHP 11 Testing Your Script Testing a PHP script is a two-step process. First, you must put the PHP script in the appropriate directory for the web server. Second, you run the PHP script in your web browser by loading the correct URL. If you’re using a separate web server, like one provided by a hosting company, you just need to use an SFTP application to upload your PHP script to it (as in the previous steps). If you have installed PHP on your personal computer, then you can test your PHP scripts by saving them in, or moving them to, the web document root. This is normally n ~/Sites for Mac OS X users (where ~ stands for your home directory; this is no longer created automatically on newer versions of Mac OS X, but you can make one) n C:\Inetpub\wwwroot for Windows users running IIS n n C:\xampp\htdocs for Windows users running XAMPP (www.apachefriends.org) /Applications/MAMP/htdocs for Mac users running MAMP (www.mamp.info) If you’re not sure what the web document root for your setup is, see the documentation for the web server application or operating system (if the web server application is built in). Once you’ve got the PHP script in the right place, use your browser to execute it. 12 Chapter 1 To test your script in the browser: 1. Open your favorite web browser. For the most part, PHP doesn’t behave differently on different browsers (because PHP runs on the server), so use whichever browser you prefer. In this book, you’ll see that I primarily use Chrome, regardless of the operating system. 2. In the browser’s address bar, enter the URL of the site where your script has been saved. In my case, I enter www.larryullman.com, but your URL will certainly be different. If you’re running PHP on your own computer, the URL is http://localhost (Windows); or http://localhost/ ~username (Mac OS X), where you should replace username with your username. Some all-in-one packages, such as MAMP and XAMPP, may also use a port as part of the URL: http:// localhost:8888. If you’re not sure what URL to use, see the documentation for the web server application you installed. 3. Add /phpinfo.php to the URL. If you placed the script within a subdirectory of the web document root, you would add that subdirectory name to the URL as well (for example, /ch01/phpinfo.php). 4. Press Return/Enter to load the URL. The page should load in your browser window A. continues on next page A If the script executed correctly, the browser result should look like this (woohoo!). Getting Started with PHP 13 If you see the PHP code B or a blank page, it could mean many things: n n n You are not loading the PHP script through a URL (that is, the address does not begin with http). Note that you may need to click the address bar to view the full URL, including the http, because many of today’s browsers hide this by default. n n You are not using the proper extension. You entered the incorrect URL. The PHP script is not in the proper directory. The PHP script does not have the correct name or extension. It’s very important to remember that you can’t open a PHP file directly in a browser as you would open HTML pages or files in other applications. PHP scripts must be processed by the web server, which means you must access them via a URL (an address that starts with http://). Even if you aren’t a seasoned computer professional, you should consider installing PHP on your computer. Doing so isn’t too difficult, and PHP is free. Again, see Appendix A for instructions. 14 code is not being executed. PHP has not been enabled on the server. If you see a file not found or similar error C, it could be because n B If you see the raw PHP code, then the PHP Chapter 1 C This server response indicates a mismatch between the URL attempted and the files that actually exist on the server. Sending Text to the Browser PHP wouldn’t be very useful if all you could do was see that it works (although that confirmation is critical). You’ll use PHP most frequently to send information to the browser in the form of plain text and HTML tags. To do so, use print: print "something"; Just type the word print, followed by what you want to display: a simple message, the value of a variable, the result of a calculation, and so forth. In that example, the message is a string of text, so it must be surrounded with quotation marks. PHP is case-insensitive when it comes to calling functions, such as phpinfo() and print. Using print, Print, and PRINT nets the same results. Later in the book, you’ll see examples where case makes a crucial difference. To be clear, print doesn’t actually print anything; it just outputs data. When a PHP script is run through a browser, that PHP output is received by the browser itself as if it were content from a static HTML file. Also note that the line is terminated by a semicolon (;). Every statement in PHP code must end with a semicolon, and forgetting this requirement is a common cause of errors. A statement in PHP is an executable line of code, like print "something"; or phpinfo(); Conversely, comments, PHP tags, control structures (for example, conditionals and loops), and certain other constructs discussed in this book don’t require semicolons. Getting Started with PHP 15 Finally, you should know about a minor technicality: Whereas phpinfo() is a function, print is actually a language construct. Although it’s still standard to refer to print as a function, because print is a language construct, no parentheses are required when using it, as in the phpinfo() example. To print a simple message: 1. Begin a new HTML document in your text editor or IDE, to be named hello1.php (Script 1.3): Hello, World!

The following was created by ➝ PHP: Most of this code is the standard HTML. The last line will be used to distinguish between the hard-coded HTML and the PHP-generated HTML. 2. On the next line, type Hello, World!

The following was created by PHP:

4. Close the PHP section and complete the HTML page: A A simple Hello, world! example: your first foray into PHP programming. ?>

5. Save the file as hello1.php, place it on your PHP-enabled server, and test it in your browser A. If you’re running PHP on your own computer, remember that you can save the file to the proper directory and access the script via http://localhost/. If you see an error or a blank page instead of the results shown in the figure, review the “Testing Your Script” section, or skip ahead to the “Basic Debugging Steps” section at the end of this chapter. You can use other functions to send text to the browser, including echo and printf(), but this book primarily uses print. You can—and commonly will—use print over multiple lines: print "This is a longer sentence of text."; The closing quotation mark terminates the message being printed, and the semicolon is placed only at the end of that line. Getting Started with PHP 17 Using the PHP Manual The PHP manual—accessible online at www.php.net/manual—lists every function and feature of the language. The manual discusses general concepts (installation, syntax, variables) first and ends with the functions by topic (MySQL, string functions, and so on). To quickly look up any function in the PHP manual, go to www.php.net/functionname in your web browser (for example, www.php.net/print). To understand how functions are described, look at the start of the print function’s page A. The first line is the name of the function itself, followed by the versions of PHP in which it’s available. As the language grows, new functions are added and, occasionally, older functions are removed. Then there’s a textual description of the function along with the function’s basic usage. The usage is the most important and confusing part. In this example, the first value—int—says that print returns an integer value (specifically, print returns 1, always). Within the parentheses, string $arg states that the function takes one required argument, which should be in the form of a string. You’ve already seen this in action. 18 Chapter 1 A The PHP manual’s page for the print language construct. As a comparison, check out the manual’s listing for the nl2br() function B. This function converts newlines found within text (the equivalent of pressing Return/ Enter) into HTML break tags. This function, which returns a string, takes a string as its first argument and an optional Boolean (TRUE/FALSE) as its second. The square brackets indicate optional arguments, which are always listed last. When a function takes multiple arguments, they are separated by commas. Hence, this function can be called like so: nl2br("Some text"); nl2br("Some text", false); B The PHP manual’s page for the nl2br() function. As the definition also indicates, the second argument has a default value of true, meaning it’ll create
tags (which is XHTML compliant) unless the function is passed a second argument value of false. In that case, the function will create
tags instead. The most important thing to remember about the PHP manual is that it exists! If you’re ever confused by a function or how it is properly used, check the PHP manual’s reference page for it. Getting Started with PHP 19 To look up a function definition: 1. Go to www.php.net/functionname in your web browser. If the PHP manual doesn’t have a matching record for the function you tried, check the spelling or look at the recommended alternatives that the manual presents C. 2. Compare the versions of PHP that the function exists in with the version of PHP you’re using. Use the phpinfo() function, already demonstrated, to know for certain what version of PHP you are running. If a function was added in a later version of PHP, you’ll need to either upgrade the version you have or use a different approach. 3. Examine what type of data the function returns. C The manual will present alternative functions if the entered URL doesn’t exactly match a reference. Sometimes you may be having a problem with a function because it returns a different type of value than you expect it to. 4. Examine how many and what types of arguments the function requires or can take. The most common mistake when using functions is sending the wrong number or type of arguments when the function is called. 5. Read the user comments, when present, to learn more. Sometimes the user comments can be quite helpful (other times not). D Deprecated functions should be avoided in your code. If you see a message saying that a function has been deprecated D, that means the function will be dropped from future versions of PHP, and you should start using the newer, better alternative (there is almost always a better alternative identified). 20 Chapter 1 A Attempting to print double quotation marks will create errors, because they conflict with the print statement’s primary double quotation marks. Script 1.4 Using print, you can send HTML tags along with text to the browser, where the formatting will be applied. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Hello, World!

The following was created by PHP: Hello, world!"; ?>

Sending HTML to the Browser As those who first learned HTML quickly discovered, viewing plain text in a web browser leaves a lot to be desired. Indeed, HTML was created to make plain text more appealing and useful. Because HTML works by adding tags to text, you can use PHP to also send HTML tags to the browser, along with other data: print "Hello, world!"; There is one situation where you have to be careful, though. HTML tags that require double quotation marks, like link, will cause problems when printed by PHP, because the print function uses quotation marks as well A: print "link"; One workaround is to escape the quotation marks within the HTML by preceding them with a backslash (\): print "link"; By escaping each quotation mark within the print statement, you tell PHP to print the mark itself instead of treating the quotation mark as either the beginning or the end of the string to be printed. To send HTML to the browser: 1. Open the hello1.php script (Script 1.3) in your text editor or IDE, if it is not already open. 2. Within the HTML head, declare a CSS class (Script 1.4): continues on next page Getting Started with PHP 21 This CSS code declares a class named bold, which will be used to add emphasis to text. This is obviously a fairly trivial use of CSS, but by declaring this as a class, it can easily be updated, perhaps to change the color of the text or the size, along with its weight. B The new version of the Hello, world! page, with a little more decoration and appeal. 3. Edit the Hello, world! message by adding HTML tags, making it read as follows: print " ➝ Hello, world!"; To make the PHP-generated part of the message stand out, CSS styling will bold the greeting. For this to work, you must escape the quotation marks within the span tag so they don’t conflict with the print statement’s quotation mark. 4. Save the script as hello2.php, place it on your PHP-enabled server, and run the page in your browser B. Using White Space When programming in PHP, white space is generally (but not universally) ignored. Any blank line (just one or several in a row) in PHP code is irrelevant to the end result. Likewise, tabs and spaces are normally inconsequential to PHP. And because PHP code is not visible in the browser (unless there’s a problem with the server), white space in your PHP files has no impact on what the end user sees. The spacing of HTML code shows up in the HTML source of a web page but has only a minimal effect on what’s viewed in the browser. For example, all of a page’s HTML source code could be placed on one line without changing what the end user sees. If you had to hunt for a problem in the HTML source, however, you would not like the long, single line of HTML. You can affect the spacing of dynamically generated HTML code by printing it in PHP over multiple lines, or by using the newline character (\n) within double quotation marks: print "Line 1\nLine 2"; Again, use of the newline character affects the HTML source code of the web page, not what the end user sees rendered in the browser. To adjust the spacing in the rendered web page, you’ll use CSS, plus paragraph, div, and break tags, among others. 22 Chapter 1 5. View the HTML page source to see the code that was sent to the browser C. How you do this depends on the browser: Select View > Developer > View Source in Chrome, View > Page Source in Firefox, or View > Source in Internet Explorer. This is a step you’ll want to be in the habit of taking, particularly when problems occur. Remember that PHP is primarily used to generate HTML, sent to and interpreted by the browser. Often, confirming what was sent to the browser (by viewing the source) will help explain the problem you’re seeing in the browser’s interpretation (or visible result). Understanding the role of quotation marks and how to escape problematic characters is crucial to programming with PHP. These topics will be covered in more detail in the next two chapters. The HTML you send to the web browser from PHP doesn’t need to be this simple. You can create tables, JavaScript, and much, much more. Remember that any HTML outside the PHP tags will automatically go to the browser. Within the PHP tags, print statements are used to send HTML to the web browser. C The resulting HTML source code of hello2.php B. Getting Started with PHP 23 Adding Comments to Scripts Comments are integral to programming, not because they do anything but because they help you remember why you did something. The computer ignores these comments when it processes the script. Furthermore, PHP comments are never sent to the browser, remaining your secret. PHP supports three ways of adding comments. You can create a single-line comment by putting either // or # at the beginning of the line you want ignored: // This is a comment. You can also use // or # to begin a comment at the end of a PHP line, like so: print "Hello"; // Just a greeting. Although it’s largely a stylistic issue, // is much more commonly used in PHP than #. You can create a multiline comment using /* to begin the comment and */ to conclude it: /* This is a multi-line comment. */ Some programmers prefer this comment style because it contains both open and closing “tags,” providing demarcation for where the comment begins and ends. 24 Chapter 1 Script 1.5 PHP and HTML comments are added to the script to document it and to render a line of PHP code inert. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Hello, World!

The following was created by PHP:
Hello, world!"; ?>

To add comments to a script: 1. Open the hello2.php created earlier (Script 1.4) in your text editor or IDE. 2. After the initial PHP tag, add some comments to your script (Script 1.5): /* * Filename: hello3.php * Book reference: Script 1.5 * Created by: Larry Ullman */ This is just a sample of the kind of comments you can write. You should document what the script does, what information it relies on, who created it, when, and so forth. Stylistically, such comments are often placed at the top of a script (as the first thing within the PHP section, that is), using formatting like this. The extra asterisks aren’t required; they just draw attention to the comments. 3. On line 21, in front of the print statement, type //. By preceding the print statement with two slashes, you ensure that the function call is “commented out,” meaning it will never be executed. 4. After the closing PHP tag (on line 23), add an HTML comment: This line of code will help you distinguish among the different comment types and where they appear. This comment will appear only within the HTML source code. continues on next page Getting Started with PHP 25 5. Save the script as hello3.php, place it on your PHP-enabled server, and run the page in your web browser A. 6. View the source of the page to see the HTML comment B. You can comment out just one line of code or several using the /* and */ method. With // or #, you can negate only one line at a time. A With the print statement commented out, the page looks just as it would if the print call weren’t there. Different programmers prefer to comment code in different ways. The important thing is to find a system that works for you and stick to it. Note that you cannot use HTML comment characters () within PHP to comment out code. You could have PHP print those tags to the browser, but in that case you’d create a comment that appeared in the HTML source code on the client’s computer (but not in the browser window). PHP comments never make it as far as a user’s computer. Despite my strong belief that you can’t over-comment your scripts, the scripts in this book aren’t as documented as they should be, in order to save space. But the book will document each script’s name and number, for cross-reference purposes. When you change a script’s code, be certain to update its comments as well. It’s quite confusing to see a comment that suggests a script or a line of code does something other than what it actually does. 26 Chapter 1 B HTML comments don’t appear in the web browser but are in the HTML source. PHP comments remain in the PHP script on the server, not visible inside the HTML source. Basic Debugging Steps Debugging is by no means a simple concept to grasp, and unfortunately, it’s one that is only truly mastered by doing. The next 50 pages could be dedicated to the subject and you’d still merely pick up a fraction of the debugging skills that you’ll eventually acquire and need. The reason I introduce debugging in this harrowing way is that it’s important not to enter into programming with delusions. Sometimes code won’t work as expected, you’ll inevitably create careless errors, and some days you’ll want to pull your hair out, even when using a comparatively userfriendly language such as PHP. In short, prepare to be perplexed and frustrated at times. I’ve been coding in PHP since 1999, and occasionally I still get stuck in the programming muck. But debugging is a very important skill to have, and one that you will eventually pick up out of necessity and experience. As you begin your PHP programming adventure, I offer the following basic but concrete debugging tips. Getting Started with PHP 27 To debug a PHP script: n n Make sure display_errors is on. This is a basic PHP configuration setting (discussed in Appendix A). You can confirm this setting by executing the phpinfo() function ( just use your browser to search for display_errors in the resulting page). For security reasons, PHP may not be set to display the errors that occur. If that’s the case, you’ll end up seeing blank pages when problems occur. To debug most problems, you’ll need to see the errors, so turn this setting on while you’re learning. You’ll find instructions for doing so in Appendix A and Chapter 3, “HTML Forms and PHP.” 28 n Chapter 1 Trust the error message. Another very common beginner’s mistake is to not fully read or trust the error that PHP reports. Although an error message can often be cryptic and may seem meaningless, it can’t be ignored. At the very least, PHP is normally correct as to the line on which the problem can be found. And if you need to relay that error message to someone else (like when you’re asking me for help), do include the entire error message! Know what version of PHP you’re running. Some problems arise from the version of PHP in use. Before you ever use any PHP-enabled server, run the phpinfo.php file (Script 1.2) to confirm the version of PHP in use. Check the HTML source code. Sometimes the problem is hidden in the HTML source of the page. In fact, sometimes the PHP error message can be hidden there! Make sure you’re always running PHP scripts through a URL! This is perhaps the most common beginner’s mistake. PHP code must be run through the web server application, which means it must be requested through http://something. When you see actual PHP code instead of the result of that code’s execution, most likely you’re not running the PHP script through a URL. n n n Take a break! So many of the programming problems I’ve encountered over the years, and the vast majority of the toughest ones, have been solved by stepping away from my computer for a while. It’s easy to become frustrated and confused, and in such situations, any further steps you take are likely to make matters only worse. These are just some general debugging techniques, specifically tailored to the beginning PHP programmer. They should suffice for now, because the examples in this book are relatively simple. More complex coding requires more advanced debugging techniques, so my PHP and MySQL for Dynamic Web Sites: Visual QuickPro Guide, Fourth Edition (Peachpit Press, 2012) dedicates a whole chapter to this subject. Review and Pursue Each chapter in this book ends with a “Review and Pursue” section. In these sections you’ll find: n n Questions regarding the material just covered Prompts for ways to expand your knowledge and experience on your own If you have any problems with these sections, in either answering the questions or pursuing your own endeavors, turn to the book’s supporting forum (www.LarryUllman.com/forums/). Review n n n n n n n What is HTML? What is the current version of HTML? What encoding is your text editor or IDE set to use? Does that match the encoding specified in your generated HTML pages? Why does the encoding matter? What is CSS and what is it used for? What file extension should PHP scripts have for your particular server? What is meant by “web root directory”? What is the web root directory for your server? How do you test PHP scripts? What happens when PHP scripts are not run through a URL? Name two ways comments can be added to PHP code. Identify some reasons to use comments. Getting Started with PHP 29 Pursue n n n n n If you have access to more than one server, confirm what version of PHP is running on another server. Create a static HTML page that displays some information. Then replace some of the static content with content created by PHP. Create a template to use for your own work. The template should contain the HTML shell, the opening and closing PHP tags, and some basic comments. Confirm, using the phpinfo() function, that display_errors is enabled on your server. If it’s not, change your server’s configuration to enable it (see Chapter 3 and Appendix A). In subsequent chapters, occasionally check the PHP manual’s page when a new function is mentioned in the book. 30 Chapter 1 2 Variables The previous chapter covered how to use PHP to send simple text and HTML to a web browser—in other words, something for which you don’t need PHP at all! Don’t worry, though; this book will teach you how to use print in conjunction with other PHP features to do great and useful things with your website. To make the leap from creating simple, static pages to dynamic web applications and interactive websites, you need variables. Understanding what variables are, the types of variables that a language supports, and how to use them is critical. This chapter introduces the fundamentals of variables in PHP, and later chapters cover the different types in greater detail. If you’ve never dealt with variables before, this chapter will be a good introduction. If you’re familiar with the concept, then you should be able to work through this chapter with ease. In This Chapter What Are Variables? 32 Variable Syntax 36 Types of Variables 38 Variable Values 41 Understanding Quotation Marks 44 Review and Pursue 48 What Are Variables? A variable is a container for data. Once data has been stored in a variable (or, stated more commonly, once a variable has been assigned a value), that data can be altered, printed to the browser, saved to a database, emailed, and so forth. Variables in PHP are, by their nature, flexible: You can put data into a variable, retrieve that data from it (without affecting the value of the variable), put new data in it, and continue this cycle as many times as necessary. But variables in PHP are largely temporary: Most only exist—that is, they only have a value—for the duration of the script’s execution on the server. Once the execution of the script completes (often when the final closing PHP tag is encountered), those variables cease to exist. Furthermore, after users click a link or submit a form, they are taken to a new page that may have an entirely separate set of variables. 32 Chapter 2 Before getting too deep into the discussion of variables, let’s write a quick script that reveals some of PHP’s predefined variables. These are variables that PHP automatically creates when a script runs. Over the course of the book, you’ll be introduced to many different predefined variables. This particular example looks at the predefined $_SERVER variable. It contains lots of information about the computer on which PHP is running. The print_r() function offers an easy way to display any variable’s value: print_r($variable_name); Just provide the name of the variable you’d like to inspect as a single argument to the print_r() function. (You’ll learn more about a variable’s syntax throughout this chapter.) Script 2.1 This script uses the print_r() function to show the values stored in the $_SERVER predefined variable. 1 2 3 4 5 6 7 8 9 10 11 Predefined Variables

To print PHP’s predefined variables: 1. Create a new PHP script in your text editor or IDE, to be named predefined.php (Script 2.1). 2. Create the initial HTML tags: Predefined Variables ➝

This code repeats the HTML template
created in the preceding chapter. Within
the body of the page, the tags
are being used to make the generated
PHP information more legible. Without
using the tags, the print_r()
function’s output would be difficult to
read in a browser.
3. Add the PHP code:

The PHP code contains just one function call. The function should be provided with the name of a variable.
In this example, the variable is
$_SERVER, which is special in PHP.
$_SERVER stores all sorts of data about
the server: its name and operating
system, the name of the current user,
information about the web server application (Apache, Nginx, IIS, and so on),
and more. It also reflects the PHP script
being executed: its name, where it’s
stored on the server, and so forth.
continues on next page

Variables

Note that you must type $_SERVER
exactly as it is here, in all uppercase letters.
4. Complete the HTML page:

5. Save the file as predefined.php,
upload it to your server (or save it to the
appropriate directory on your computer), and test it in your browser A.
Once again, remember that you must
run all PHP scripts through a URL (that
is, http://something).

6. If possible, transfer the file to another
computer or server running PHP and
execute the script in your browser
again B.
Printing out the value of any variable
as you’ve done here is one of the greatest
debugging tools. Scripts often don’t work
as you expect them to because one or more
variables do not have the values you assume
they should, so confirming their actual values
is extremely helpful.
If you don’t use the HTML
tags, the result will be like the jumble of information in C.

A The $_SERVER variable, as printed out by this script, is a master list
of values pertaining to the server and the PHP script.
34

Chapter 2

B With the predefined.php page, different servers will generate different
results (compare with A).

C With large, complex variables such as $_SERVER, not using the HTML
preformatting tags with print_r() creates an incomprehensible mess
(compare to A B).
Variables

Variable Syntax
Now that you’ve had a quick dip in the variable pool, it’s time to swim a bit deeper. In
the preceding example, the script printed
out the value of PHP’s predefined $_SERVER
variable. You can also create your own
variables, once you understand the proper
syntax. To create appropriate variable
names, you must follow these rules:
n

All variable names must be preceded
by a dollar sign ($).
Following the dollar sign, the variable
name must begin with either a letter
(A–Z, a–z) or an underscore (_). A number cannot immediately follow the
dollar sign.
The rest of the variable name can contain any combination of letters, underscores, and numbers.
You may not use spaces within the
name of a variable. (Instead, the underscore is commonly used to separate
words.)
Each variable must have a unique
name.
Variable names are case-sensitive!
Consequently, $variable and
$Variable are two different constructs,
and it would be a bad idea to use two
variables with such similar names.

This last point is perhaps the most important:
Variable names in PHP are case-sensitive.
Using the wrong letter case is a very
common cause of bugs. (If you used, for
example, $_server or $_Server in the
previous script, you’d see either an error
message or nothing at all A.)

36 Chapter 2

A Misspelling a variable’s name, including its
case, will create undesired and unpredictable
results.

Script 2.2 Properly documenting the purposes of
variables, along with using meaningful names, is a
hallmark of a professional programmer.

To help minimize bugs, I recommend the
following policies:
n

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18

Variables and Comments

TABLE 2.1 Valid Variables in PHP
Name

Always use all lowercase variable names.
Make your variable names descriptive
(for example, $first_name is better
than $fn).
Use comments to indicate the purpose
of variables (Script 2.2), redundant as
that may seem.
Above all, be consistent with whatever
naming convention you choose!

Table 2.1 lists some sample valid variables;
Table 2.2 lists some invalid variables and
the rules they violate.
Unlike some other languages, PHP
doesn’t require you to declare or initialize a
variable prior to use, although PHP does issue
warnings when you do. In other words, you
can refer to variables without first defining
them. But it’s best not to do that; try to write
scripts so that every variable is defined or
validated before use.
There are two main variable naming
conventions, determined by how you delineate
words. These are the so-called camel-hump
or camel-case (named because of the way
capital letters break up the word—for example,
$FirstName) and underscore ($first_name)
styles. This book uses the latter convention.

$first_name
$person
$address1
$_SERVER

TABLE 2.2 Invalid Variables in PHP
Name

Reason

$first name

Has a space

$first.name

Has a period

first_name

Does not begin with $

$1address

A number cannot follow $

Variables

Types of Variables
This book covers three common PHP variable types: numbers, strings, and arrays.
This chapter introduces them quickly, and
later chapters discuss them in more detail:
n

Chapter 4, “Using Numbers”

Chapter 5, “Using Strings”

Chapter 7, “Using Arrays”

A fourth variable type, objects, is introduced in Appendix B, “Resources and Next
Steps,” but isn’t covered in this book. That
particular subject is just too advanced for
a beginner’s guide—in fact, basic coverage
of the subject in my PHP Advanced and
Object-Oriented Programing: Visual
QuickPro Guide, Third Edition (Peachpit
Press, 2013) requires over 150 pages!

Numbers
Technically speaking, PHP breaks numbers
into two types: integers and floating-point
(also known as double-precision floatingpoint or doubles). Due to the lax way PHP
handles variables, it largely won’t affect your
programming to group the two categories
of numbers into one all-inclusive membership, at least when you’re just starting out.
Still, let’s briefly discuss the differences
between the two, to be precise.
The first type of numbers—integers—is also
known as whole numbers. They can be positive or negative but include neither fractions
nor decimals. Numbers that use a decimal
point (even something like 1.0) are floatingpoint numbers, also known as floats. You
use floating-point numbers to refer to fractions, because the only way to express a
fraction in PHP is to convert it to its decimal
equivalent. Hence, 1¼ is written as 1.25.
Table 2.3 lists some sample valid numbers
and their formal type; Table 2.4 lists invalid
numbers and the rules they violate.
As you’ll soon see, you add quotation
marks around invalid numbers to turn them
into valid strings.

TABLE 2.3 Valid Numbers in PHP

TABLE 2.4 Invalid Numbers in PHP

Number

Type

Number

Reason

Integer

1/3

Contains a slash

1.0

Floating-point

1996a

Contains a letter

1972

Integer

08.02.06

19.72

Floating-point

Contains multiple
decimals

–1

Integer

–1.0

Floating-point

Chapter 2

Strings
A string is any number of characters
enclosed within a pair of either single (')
or double (") quotation marks. Strings can
contain any combination of characters
that exist: letters, numbers, symbols, and
spaces. Strings can also contain variables.
Here are examples of valid string values:
"Hello, world!"
"Hello, $first_name!"
"1/3"
'Hello, world! How are you today?'
"08.02.06"
"1996"
''

That last example is an empty string—a
string that contains no characters.
To create a string, just wrap 0 or more
characters within quotation marks. There
are cases, however, where you may run
into problems. For example:
"I said, "How are you?""

This string will be tricky. Chapter 1, “Getting
Started with PHP,” hinted at the same problem with respect to printing HTML code.
When PHP hits the second quotation mark
in the example, it assumes the string ends
there; the continuing text (How…) causes
an error. To use a quotation mark within a
string you escape the quotation mark by
putting a backslash (\) before it:

The backslash tells PHP to treat each
escaped quotation mark as part of the
value of the string, rather than using it as
the string’s opening or closing indicators.
You can similarly circumvent this problem
by using different quotation mark types:
'I said, "How are you?"'
"I said, 'How are you?'"
Notice that “1996” converts an integer
into a string, simply by placing the number
within quotes. Essentially, the string contains
the characters 1996, whereas the number (a
nonquoted value) would be equal to 1996. It’s
a fine distinction, and one that won’t matter
in your code, because PHP lets you perform
mathematical calculations with the string 1996
just as you can with the number.
Chapter 1 also demonstrated how to
create a new line by printing the \n character within double quotation marks. Although
escaping a quotation mark prints the quotation mark, escaping an n prints a new line,
escaping an r creates a carriage return, and
escaping a t creates a tab.
Understanding strings, variables, and the
single and double quotation marks is critical
to programming with PHP. For this reason, a
section at the end of this chapter is dedicated
to the subject.

"I said, \"How are you?\""

Variables

Arrays
Arrays are covered more thoroughly in
Chapter 7, but let’s look at them briefly
here. Whereas a string or a number contains a single value (both are said to be
scalar), an array can have more than one
value assigned to it. You can think of an
array as a list or table of values: You can
put multiple strings and/or numbers into
one array.
Arrays use keys to create and retrieve the
values they store. The resulting structure—
a list of key-value pairs—is similar to a
two-column spreadsheet. Unlike arrays in
other programming languages, the array
structure in PHP is so flexible that it can use
either numbers or strings for both the keys
and the values. The array doesn’t even need
to be consistent in this respect. (All of this
will make more sense in Chapter 7, when
you start working with specific examples.)
PHP supports two kinds of arrays, based
on the format of the keys. If the array uses
numbers for the keys (Table 2.5), it’s known
as an indexed array. If it uses strings for
the keys (Table 2.6), it’s an associative
array. In either case, the values in the array
can be of any variable type (string, number,
and so on).
The array’s key is also referred to as
its index. You’ll see these two terms used
interchangeably.
An array can, and frequently will, contain
other arrays, creating what is called a multidimensional array.
What PHP refers to as an associative
array is known as a hash in Perl and Ruby,
among other languages.

Chapter 2

TABLE 2.5 Indexed Array
Key

Value

Dev

Rachel

Denise

Arnold

TABLE 2.6 Associative Array
Key

Value

Vermont

New Hampshire

Iowa

Pennsylvania

Variable Values
A The result of printing the values
of two variables.

To assign a value to a variable, regardless
of the variable type, you use the equals
sign (=). Therefore, the equals sign is known
as the assignment operator, because it
assigns the value on the right to the variable
on the left. For example:
$number = 1;
$floating_number = 1.2;
$string = "Hello, world!";

B Using the print statement on a complex

variable type, such as an array, will not have the
results you desire.

Each of these lines represents a complete
statement (that is, an executable action),
so each concludes with a semicolon.
To print the value of a variable, use the
print function:
print $number;
print $string;

If you want to print a variable’s value within
a context, you can place the variable’s
name in the printed string, as long as you
use double quotation marks A:
print "Number is $number";
print "String is $string";

Using print in this way works for the scalar (single-valued) variable types—numbers
and strings. For complex variable types—
arrays and objects—you cannot just use
print B:
print "_SERVER is $_SERVER";

As you’ve already seen, print_r() can
handle these nonscalar types, and you’ll
learn other approaches later in the book.
Whether you’re dealing with scalar or nonscalar variables, don’t forget that printing
out their values is an excellent debugging
technique when you’re having problems
with a script.

Variables 41

Because variable types aren’t locked in
(PHP is referred to as a weakly typed language), they can be changed on the fly:
$variable = 1;
$variable = "Greetings";

If you were to print the value of $variable
now, the result would be Greetings. The
following section better demonstrates the
concept of assigning values to variables
and then accessing those values.

To assign values to and
access variables:
1. Create a new PHP script in your
text editor or IDE, to be named
variables.php (Script 2.3).
2. Create the initial HTML tags:

Variables

3. Begin the PHP code:

Variables

The address is:
$street

$city $state $zip";

Remember that each statement must
conclude with a semicolon and that the
variable names are case-sensitive.
5. Print out the values of the variables
within some context:

C Some variables are assigned values, and then
printed within a context.

D Parse errors are the most common type of PHP
error, as you’ll discover. They’re frequently caused
by missing semicolons or mismatched quotation
marks or parentheses.

print "The address is:
➝
$street
$city $state
➝ $zip";

Here a single print statement references all the variables. The entire string
to be printed (consisting of text, HTML
tags, and variables) is enclosed within
double quotation marks. The HTML

tags make the text flow over multiple lines in the browser.
6. Complete the PHP section and the
HTML page:
?>

E The Undefined variable error indicates that

you used a variable with no value (it hasn’t been
defined). This can happen with misspellings and
capitalization inconsistencies.

7. Save the file as variables.php, upload
it to your server (or save it to the appropriate directory on your computer), and
test it in your browser C.
If you see a parse error D when you
run this script, you probably either omitted
a semicolon or have an imbalance in your
quotation marks. In such particular cases, the
mistake itself is likely on the previous line of
code (than reported in the error message) but
wasn’t caught by PHP until the next line.
If one of the variable’s values isn’t
printed out or you see an Undefined variable
error E, you most likely failed to spell a
variable name the same way twice.
If you see a blank page, you most likely
have an error but PHP’s display_errors
configuration is set to off. See Chapter 3,
“HTML Forms and PHP,” for details.

Variables

Understanding
Quotation Marks
Now that you know the basics of variables
and how to create them, let’s do an exercise to make sure you completely understand how to properly use quotation marks.
PHP, like most programming languages,
allows you to use both double (") and
single (') quotation marks—but they give
vastly different results. It’s critical that you
comprehend the distinction, so the next
example will run tests using both types just
to emphasize the different behaviors.
The rule to remember is: Items within
single quotation marks are treated literally;
items within double quotation marks
are extrapolated. This means that within
double quotation marks, a variable’s name
is replaced with its value, as in Script 2.3,
but the same is not true for single quotation marks.
This rule applies anywhere in PHP you
might use quotation marks, including
uses of the print function and the assignment of values to string variables. An
example is the best way to demonstrate
this critical concept.

Chapter 2

Script 2.4 This script simply demonstrates how
the type of quotation mark you use with variables
affects the result.
1
2
3
4
5
6
7
8
9
10

Quotes

Double Quotes
name1 is $name1

name2 is $name2";
print 'Single Quotes
name1 is $name1

name2 is $name2';

To use quotation marks:
1. Begin a new PHP script in your text
editor or IDE, to be named quotes.php
(Script 2.4).
2. Create the initial HTML tags:

Quotes

3. Begin the PHP code:
Double Quotes
name1 is $name1

name2 is $name2";
print 'Single Quotes
name1 is $name1

name2 is $name2';

Again, the quotation marks make all the
difference here. The first print statement, using double quotation marks,
prints out the values of the $name1 and
$name2 variables, whereas the second,
using single quotation marks, prints out
$name1 and $name2 literally.
The HTML in the print statements
makes them more legible in the
browser. Each statement is executed
over three lines of PHP code for additional readability, which is perfectly
acceptable.

Chapter 2

7. Complete the PHP section and the
HTML page:
?>

8. Save the file as quotes.php, upload it
to your server (or save it to the appropriate directory on your computer), and
test it in your browser A.

A The different quotation marks (single
versus double) dictate whether the
variable’s name or value is printed.

If you’re still confused about the distinction between the two types of quotation marks,
always stick with double quotation marks and
you’ll be safer.
Arguably, using single quotation marks
when you can is marginally preferable, because
PHP won’t need to search the strings looking
for variables, resulting in better performance.
But, at best, this is a minor optimization.
The shortcuts for creating newlines (\n),
carriage returns (\r), and tabs (\t) must be
used within double quotation marks to have
the desired effect. Within single quotes, each
of those is treated literally.
Remember that you don’t always need to
use quotation marks at all. When assigning a
numeric value or when only printing a variable,
you can omit them:

$num = 2;
print $num;

Variables 47

Review and Pursue
If you have any problems with the review
questions or the pursue prompts, turn
to the book’s supporting forum
(www.LarryUllman.com/forums/).

Review
n

n
n

What kind of variable is $_SERVER an
example of?
What character must all variables
begin with?
What characters can be used in a variable’s name (after the required initial
character)? What other characters can
be used in a variable’s name, after the
first character?
Are variable names case-sensitive or
case-insensitive?
What does it mean to say that a variable
is scalar? What are examples of scalar
variable types? What is an example of
a nonscalar variable type?
What is the assignment operator?
What great debugging technique—with
respect to variables—was introduced
in this chapter?
What is the difference between using
single and double quotation marks?

Pursue
n

Create another PHP script that defines
some variables and prints their values.
Try using variables of different scalar
types.
Create a PHP script that prints the value
of some variables within some HTML.
More sophisticated practice might
involve using PHP and variables to
create a link or image tag.

48 Chapter 2

3
HTML Forms
and PHP
The previous chapter provided a brief
introduction to the topic of variables.
Although you’ll commonly create your
own variables, you’ll also frequently use
variables in conjunction with HTML forms.
Forms are a fundamental unit of websites,
enabling such features as registration
and login systems, search capability, and
online shopping. Even the simplest site
will find logical reasons to incorporate
HTML forms. And with PHP, it’s stunningly
simple to receive and handle data generated by them.
With that in mind, this chapter will cover
the basics of creating HTML forms and
explain how the submitted form data is
available to a PHP script. This chapter will
also introduce several key concepts of real
PHP programming, including how to manage errors in your scripts.

In This Chapter
Creating a Simple Form

Choosing a Form Method

Receiving Form Data in PHP

Displaying Errors

Error Reporting

Manually Sending Data to a Page

Review and Pursue

Creating a
Simple Form
For the HTML form example in this chapter,
you’ll create a feedback page that takes
the user’s salutation (or title), name, email
address, response, and comments A. The
code that generates a form goes between
opening and closing form tags:

form elements

The form tags dictate where a form begins
and ends. Every element of the form must
be entered between these two tags. The
opening form tag should also contain an
action attribute. It indicates the page to
which the form data should be submitted.
This value is one of the most important
considerations when you’re creating a form.
In this book, the action attributes will
always point to PHP scripts:

Before creating this next form, let’s briefly
revisit the topic of HTML5. HTML5 introduces some new form element types, such
as email, number, and url. These types,
which are generally well supported by
current browsers, provide additional benefits over a simple text input, including:
n

uilt-in browser-based validation (for
B
example, the browser will check that
entered text is a syntactically valid email
address or URL).
etter user experience (for example,
B
an email address-specific keyboard
presented to mobile users).

HTML5 also introduces a required attribute
that prevents a form from being submitted
without a value entered or selected B.

50 Chapter 3

A The HTML form that will be used in this
chapter’s examples.

B The required attribute validates—in the

browser—that a selection was made or content
was entered.

Script 3.1 This HTML page has a form with several
different input types.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17

18
19

20
21
22

23
24

25
26

27
28
29
30
31
32
33

<!doctype html>

Feedback Form

Please complete this form to
submit your feedback:

p>Name:

p>Email Address:
p>Response: This is...
<
excellent
okay

boring
p>Comments:

As a final note, give each form element its
own unique name. Stick to a consistent
naming convention when naming elements,
using only letters, numbers, and the underscore (_). The result should be names that
are also logical and descriptive.

To create a basic HTML form:
1. B
egin a new document in your text editor
or IDE, to be named feedback.html
(Script 3.1):

Feedback Form

Please complete this
➝ form to submit your feedback:
➝

2. Add the opening form tag:

The form tag indicates that this form
will be submitted to the page handle_
form.php, found within the same directory as this HTML page. You can use a
full URL to the PHP script, if you’d prefer
to be explicit (for example, http://
www.example.com/handle_form.php).
continues on next page

input type="submit" name="submit"
<
value="Send My Feedback">

</div>

HTML Forms and PHP

3. A
dd a select menu plus a text input for
the person’s name:
Name:
➝

The inputs for the person’s name will
consist of two elements A. The first is
a drop-down menu of common titles:
Mr., Mrs., and Ms. Each option listed
between the select tags is an answer
the user can choose C. The second
element is a basic text box for the
person’s full name. Arguably, this list
should be expanded, or you could
use a text input to let users enter their
preferred title.
Every form element, except for the submit
button, will have the required attribute.
4. A
dd a text input for the user’s email
address:
Email Address:

The email input type is new in HTML5.
On browsers that support it—all the
most recent ones—client-side validation
is automatic D.

Chapter 3

C The select element creates a drop-down menu
of options.

D The email input type, new in HTML5, validates
the syntax of the entered text against what’s
required for email addresses.

5. Add radio buttons for a response:
Response: This is...

➝ excellent

➝ okay
boring

This HTML code creates three radio
buttons (clickable circles, A). Because
they all have the same value for the
name attribute, only one of the three
can be selected at a time. Adding the
required attribute to any one of them
makes selection of one of them a
requirement.
dd a textarea to record the
6. A
comments:
Comments: ➝

A textarea gives users more space to
enter their comments than a text input
would. However, the text input lets
you limit how much information users
can enter, which you can’t do with the
textarea (not without using JavaScript,
that is). When you’re creating a form,
choose input types appropriate to the
information you wish to retrieve from
the user.
Note that a textarea does have a closing tag, unlike the text input type.

7. Add the submit button:

The value attribute of a submit input
is what appears on the button in the
browser A. You could also use Go! or
Submit, for example.
8. Close the form:

9. C
omplete the page:

10. S
ave the page as feedback.html, and
view it in your browser.
Because this is an HTML page, not a
PHP script, you could view it in your
browser directly from your computer.
Note that feedback.html uses the
HTML extension because it’s a standard HTML
page (not a PHP script). You could use the .php
extension without a problem, even though
there’s no actual PHP code. (Remember that
in a PHP page, anything not within the PHP
tags——is assumed to be HTML.)
Be certain that your action attribute
correctly points to an existing file on the server,
or your form won’t be processed properly.
In this case, the form will be submitted to
handle_form.php, to be located in the same
directory as the feedback.html page.
In this example, an HTML form is created
by hand-coding the HTML, but you can do
this in a webpage application (such as Adobe
Dreamweaver) if you’re more comfortable with
that approach.

HTML Forms and PHP

Choosing a
Form Method
The experienced HTML developer will
notice that the feedback form just created
is missing one thing: The initial form tag
has no method attribute. The method attribute tells the server how to transmit the
data from the form to the handling script.
You have two choices with method: GET
and POST. With respect to forms, the difference between using GET and POST is
squarely in how the information is passed
from the form to the processing script. The
GET method sends all the gathered information along as part of the URL. The POST
method transmits the information invisibly
to the user. For example, upon submitting
a form, if you use the GET method, the
resulting URL will be something like
http://example.com/page.php?var=
➝ value&age=20&...

Following the name of the script, page.php,
is a question mark, followed by one
name=value pair for each piece of data
submitted.
When using the POST method, the end
user will only see
http://example.com/page.php.

Chapter 3

When deciding which method to use, keep
in mind these four factors:
n

A If users refresh a PHP script that data has been
sent to via the POST method, they will be asked to
confirm the action (the specific message will differ
depending on the browser).
n

ith the GET method, a limited amount
W
of information can be passed.
he GET method sends the data to the
T
handling script publicly (which means,
for example, that a password entered
in a form would be viewable by anyone
within eyesight of the browser, creating
a larger security risk).
page generated by a form that used
A
the GET method can be bookmarked,
but one based on POST can’t be.
sers will be prompted if they attempt
U
to reload a page accessed via POST A,
but will not be prompted for pages
accessed via GET.

Generally speaking, GET requests are used
when asking for information from the server.
Search pages almost always use GET (check
out the URLs the next time you use a search
engine), as do sites that paginate results
(like the ability to browse categories of
products). POST is normally used to trigger
a server-based action. This might be the
submission of a contact form (result: an
email gets sent) or the submission of a blog’s
comment form (result: a comment is added
to the database and therefore the page).
This book uses POST almost exclusively for
handling forms, although you’ll also see a
useful technique involving the GET method
(see “Manually Sending Data to a Page” at
the end of this chapter).

HTML Forms and PHP

To add a method to a form:
1. O
pen feedback.html (Script 3.1) in your
text editor or IDE, if it is not already
open.
2. Within the initial form tag, add
method="post" (Script 3.2, line 11).
The form’s method attribute tells the
browser how to send the form data to
the receiving script. Because there may
be a lot of data in the form’s submission
(including the comments), and because
it wouldn’t make sense for the user to
bookmark the resulting page, POST is
the logical method to use.
3. S
ave the script and reload it in your
browser.
It’s important that you get in the habit
of reloading pages in the browser after
you make changes. It’s quite easy to
forget the reloading step and find yourself flummoxed when your changes are
not being reflected.

Script 3.2 Adding a method attribute with a value
of post completes the form.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26

27
28
29
30
31
32
33

56 Chapter 3

<!doctype html>

Feedback Form

Please complete this form to
submit your feedback:
form action="handle_form.php"
<
method="post">

<p>Name:
<p>Email Address:
<p>Response: This is...
excellent
okay
boring
<p>Comments:
<input type="submit" name="submit"
value="Send My Feedback">
</form>

4. V
iew the source of the page to make sure
all the required elements are present
and have the correct attributes B.
In the discussion of the methods, GET
and POST are written in capital letters to
make them stand out. However, the form in
the script uses post. Don’t worry about this
inconsistency (if you caught it at all)—the
method will work regardless of case.

B With forms, much of the important information, such as the action and method values or
element names, can be seen only within the HTML source code.

HTML Forms and PHP 57

Receiving
Form Data in PHP
Now that you’ve created a basic HTML
form capable of taking input from a user,
you need to write the PHP script that will
receive and process the submitted form
data. For this example, the PHP script will
simply repeat what the user entered into
the form. In later chapters, you’ll learn how
to take this information and store it in a
database, send it in an email, write it to a
file, and so forth.
To access the submitted form data, you need
to refer to a particular predefined variable.
Chapter 2, “Variables,” already introduced
one predefined variable: $_SERVER. When
it comes to handling form data, the specific
variable the PHP script would refer to is
either $_GET or $_POST. If an HTML form
uses the GET method, the submitted form
data will be found in $_GET. When an HTML
form uses the POST method, the submitted
form data will be found in $_POST.
$_GET and $_POST, besides being predefined

variables (that is, ones you don’t need to
create), are arrays, a special variable type
($_SERVER is also an array). This means
that both $_GET and $_POST may contain
numerous values, making the printing of
those values more challenging. You cannot
treat arrays like so:

(Also see B under “Variable Values” in
Chapter 2 for the result of the previous code.)
Instead, to access a specific value, you
must refer to the array’s index or key.
Chapter 7, “Using Arrays,” goes into this
subject in detail, but the premise is simple.
Start with a form element whose name attribute has a value of address:

Then, assuming that the form uses the
POST method, the value entered into
that form element would be available in
$_POST['address']:
print $_POST['address'];

Unfortunately, there is one little hitch here:
When used within double quotation marks,
the single quotation marks around the key
will cause parse errors A:
print "You provided your address as:
➝ $_POST['address']";

You can avoid this problem in a couple of
ways. This chapter will use the solution
that’s syntactically the simpler of the two:
just assign the particular $_POST element
to another variable first:
$something = $_POST['something'];
➝ print "Thanks for saying:
➝ $something";

In Chapter 7 you’ll learn another approach.

print $_POST; // Will not work!

A This ugly parse error is created by attempting to use $_POST['address']
within double quotation marks.

58 Chapter 3

Script 3.3 Form data submitted to the script is
displayed by referencing the associated $_POST
variables.
1
2
3
4
5
6
7
8
9
10
11

12
13
14
15
16
17
18
19
20
21

22
23
24
25

<!doctype html>

Your Feedback

Thank you, $title $name,
p
for your comments.
You stated that you found this

example to be '$response' and
added:
$comments";

Two final notes before implementing this
information in a new PHP script: First, as
with all variables in PHP, $_POST is case
sensitive; it must be typed exactly as you
see it here (a dollar sign, one underscore,
then all capital letters). Second, the indexes
in $_POST—something in the preceding
example—must exactly match the values
of the name attributes in the corresponding
form element.

To handle an HTML form:
1. B
egin a new document in your
text editor or IDE, to be named
handle_form.php (Script 3.3):

Your Feedback

2. A
dd the opening PHP tag and any
comments:
Thank you, $title
➝ $name, for your comments.
You stated that you found
➝ this example to be '$response'
➝ and added:
$comments";

This one print statement uses the four
variables within a context to show the
user what data the script received.
lose the PHP section, and complete
5. C
the HTML page:
?>

60 Chapter 3

6. Save the script as handle_form.php.
Note that the name of this file must
exactly match the value of the action
attribute in the form.
pload the script to the server (or store
7. U
it in the proper directory on your computer if you’ve installed PHP), making
sure it’s saved in the same directory as
feedback.html.

B Whatever the user enters into the HTML form
should be printed out to the browser by the
handle_form.php script C.

8. L oad feedback.html in your browser
through a URL (http://something).
You must load the HTML form through
a URL so that when it’s submitted to
the PHP script, that PHP script is also
run through a URL. PHP scripts must
always be run through a URL!
Failure to load a form through a URL is
a common beginner’s mistake.
9. Fill out B, and then submit the form C.

C This is another application of the print
statement discussed in Chapter 1, but it constitutes
your first dynamically generated web page.

D Notices like these occur when a script refers

If you see a blank page, read the next
section of the chapter for how to display
the errors that presumably occurred.
If you see an error notice D or see that
a variable does not have a value when
printed, you likely misspelled either
the form element’s name value or the
$_POST array’s index (or you filled out
the form incompletely).

to a variable that doesn’t exist. In this particular
case, the cause is erroneously referring to
$_POST['Name'] when it should be $_POST['name'].

HTML Forms and PHP

If you want to pass a preset value along
to a PHP script, use the hidden type of input
within your HTML form. For example, inserting

between the form tags will create a variable
in the handling script named
$_POST['form_page'] with the value
feedback.html.
Notice that the value of radio button and
certain menu variables is based on the value
attribute of the selected item (for example,
excellent from the radio button). This is also
true for checkboxes. For text boxes, the value
of the variable is what the user typed.
If the handle_form.php script displays
extra slashes in submitted strings, see the
“Magic Quotes” sidebar for an explanation
and solution.

Magic Quotes
Earlier versions of PHP had a feature
known as Magic Quotes, which has
since been removed (as of PHP 5.4).
Magic Quotes—when enabled—automatically escapes single and double
quotation marks found in submitted form
data. So the string I’d like more information would be turned into I\’d like more
information.
The escaping of potentially problematic characters can be useful and even
necessary in some situations. But if the
Magic Quotes feature is enabled on your
PHP installation, you’ll see these backslashes when the PHP script prints out
the form data. You can undo its effect
using the stripslashes() function. To
apply it to the handle_form.php script,
you would do this, for example:

As a brute-force way of seeing all the
form data submitted to a PHP script, call
print_r($_POST), in the same way that
Chapter 2 calls print_r() with $_SERVER.

$comments = stripslashes
➝ ($_POST['comments']);

You can also access form data, regardless of the form’s method, in the $_REQUEST
predefined variable. $_GET and $_POST
are more precise, however, and therefore
preferable.

$comments = $_POST['comments'];

Chapter 3

instead of just this:
That will have the effect of converting
an escaped submitted string back to its
original, non-escaped value.
If you’re not seeing extraneous slashes
added to submitted form data, you don’t
need to worry about Magic Quotes.

Displaying Errors
One of the very first issues that arise when
it comes to debugging PHP scripts is that
you may not even see the errors that occur.
After you install PHP on a web server, it
will run under a default configuration with
respect to security, performance, how it
handles data, and so forth. One of the
default settings is to not display any errors.
In other words, the display_errors setting
will be off A. When that’s the case, what
you might see when a script has an error
is a blank page. (This is common on fresh
installations of PHP; most hosting companies
will enable display_errors.)
The reason that errors should not be
displayed on a live site is that it’s a security
risk. Simply put, PHP’s errors often give
away too much information for the public at
large to see (not to mention that showing
PHP errors looks unprofessional). But you,
the developer, do need to see these errors
in order to fix them!

To have PHP display errors, you can do
one of the following:
n

Turn display_errors back on for PHP
as a whole. (See the “Configuring PHP”
section of Appendix A, “Installation and
Configuration,” for more information.)
Turn display_errors back on for an
individual script.

While developing a site, the first option is
by far preferred. However, it’s a possibility
only for those with administrative control
over the server. But anyone can use the
second option by including this line in a script:
ini_set('display_errors', 1);

The ini_set() function allows a script to
temporarily override a setting in PHP’s configuration file (many, but not all, settings can
be altered this way). The previous example
changes the display_errors setting to
on, which is represented by the number 1.
Although this second method can be
implemented by anyone, the downside is
that if your script contains certain kinds of
errors (discussed next), the script cannot
be executed. In that situation, this line of
code won’t be executed, and the particular
error—or any that prevents a script from
running at all—still results in a blank page.

A Run a phpinfo() script (for example, Script 1.2) to view your server’s display_errors setting.

HTML Forms and PHP

To display errors in a script:
1. O
pen handle_form.php in your text
editor or IDE, if it is not already open.
2. A
s the first line of PHP code, enter the
following (Script 3.4):
ini_set('display_errors', 1);

Again, this line tells PHP you’d like to
see any errors that occur. You should
call it first thing in your PHP section so
the rest of the PHP code will abide by
this new setting.

Script 3.4 This addition to the PHP script turns on
the display_errors directive so that errors will be
shown.
1
2
3
4
5
6
7
8
9
10

3. Save the file as handle_form.php.

11
12

4. U
pload the file to your web server, and
test it in your browser.

If the resulting page has no errors in it,
then the script will run as it did before.
If you saw a blank page when you ran
the form earlier, you should now see
the actual error messages (like those in
D in the previous section). Again, if you
see such errors, you likely misspelled
the name of a form element, misspelled
the index in the $_POST array, or didn’t
fill out the form completely.

14
15
16
17
18
19
20
21
22
23

Make sure display_errors is enabled
anytime you’re having difficulties debugging
a script. If you installed PHP on your computer,
I highly recommend enabling it in your PHP
configuration while you learn (again, see
Appendix A).
If you see a blank page when running a
PHP script, also check the HTML source code
for errors or other problems.
Remember that the display_errors
directive only controls whether error messages
are sent to the browser. It doesn’t create errors
or prevent them from occurring in any way.
Failure to use an equals sign after name
in a form element will also cause problems:

Chapter 3

24
25
26
27

<!doctype html>

Your Feedback

Thank you, $title $name, for
your comments.
You stated that you found this
example to be '$response' and
added:
$comments";
?>

Error Reporting
Another PHP configuration issue you should
be aware of, along with display_errors,
is error reporting. PHP has more than a
dozen different levels of errors, and you
can define your own (a subject not covered
in this book). Table 3.1 lists the four most
important general error levels, along with a
description and example of each.
You can set what errors PHP reports on in
two ways. First, you can adjust the error_
reporting level in PHP’s configuration file

(again, see Appendix A). If you are running
your own PHP server, you’ll probably want
to adjust that global setting while developing your scripts.
The second option is to use the error_
reporting() function in a script. The
function takes either a number or one or
more constants—nonquoted strings with
predetermined meanings—to adjust the
levels. (Each constant is associated with a
number.) The most important of these constants are listed in Table 3.2, in order from
most forgiving to least.

TABLE 3.1 PHP Error Levels
Type

Description

Example

Notice

Nonfatal error that may or may not be
indicative of a problem

Referring to a variable that has no value

Warning

Nonfatal error that is most likely problematic

Misusing a function

Parse error

Fatal error caused by a syntactical mistake

Omission of a semicolon or an imbalance
of quotation marks, braces, or parentheses

Error

A general fatal error

Memory allocation problem

TABLE 3.2 Error Reporting Constants
Name

E_ERROR
E_WARNING
E_PARSE
E_NOTICE
E_STRICT
E_DEPRECATED

HTML Forms and PHP

Using this information, you could add any
of the following to a script:
error_reporting(E_WARNINGS);
error_reporting(E_ALL);
error_reporting(E_ALL & ~E_STRICT);

The first line says that only warnings and
below should be reported. The second
requests that all errors be reported. The
last example states that you want to see
all error messages except strict ones (the
& ~ means and not). E_STRICT also notifies
you of code that could be problematic in
certain environments or future versions of
PHP. Keep in mind that adjusting this setting doesn’t prevent or create errors; it just
affects whether or not errors are reported.
It’s generally best to develop and test PHP
scripts using the highest level of error reporting possible. To accomplish that, declare
that you want all errors error reporting:
error_reporting(E_ALL);

Otherwise, the default level of error reporting (as of this writing) is E_ALL & ~E_NOTICE
& ~E_STRICT & ~E_DEPRECATED. Unless you
override this default setting, you will not be
told about notices, strict errors, and deprecated code. As a developer, you want to be
notified of any potential or actual problem
with your code.
Let’s apply this adjustment to the handle_
form.php page.

To adjust error reporting in a script:
1. O
pen handle_form.php (Script 3.4) in
your text editor or IDE, if it is not open
already.
2. A
fter the ini_set() line, add the
following (Script 3.5):
error_reporting(E_ALL);

66 Chapter 3

Script 3.5 Adjust a script’s level of error reporting
to give you more or less feedback on potential and
existing problems. In my opinion, more is always
better.
1
2
3
4
5
6
7
8
9
10

<!doctype html>

Your Feedback

Thank you, $title $name, for
your comments.
You stated that you found this
example to be '$response' and
added:
$comments";
?>

3. Save the file as handle_form.php.
4. P
lace the file in the proper directory for
your PHP-enabled server, and test it in
your browser by submitting the form
(A and B).
At this point, if the form is filled out
completely and the $_POST indexes
exactly match the names of the form
elements, you shouldn’t see any errors
(as in the figures). If any problems
exist, including any potential problems
(thanks to E_STRICT), they should be
displayed and reported.

A Try the form one more time…
The PHP manual lists all the errorreporting levels, but those listed here are the
most important.
The code in this book was tested using
the highest level of error reporting: E_ALL.

B …and here’s the result (if filled out completely
and without any programmer errors).

Prior to PHP 5.4.0, E_STRICT was not
included in E_ALL, so the highest level of error
reporting could be achieved using

error_reporting(E_ALL | E_STRICT);
The vertical bar, known as the pipe, is the
equivalent of an “or” conditional.

HTML Forms and PHP 67

Manually Sending
Data to a Page
The last example for this chapter is a
slight tangent to the other topics but plays
off the idea of handling form data with
PHP. As discussed in the earlier section
“Choosing a Form Method,” if a form uses
the GET method, the resulting URL is
something like
http://example.com/page.php?
➝ var=value&age=20&...

The receiving page (here, page.php) is
sent a series of name=value pairs, each of
which is separated by an ampersand (&).
The whole sequence is preceded by
a question mark (immediately after the
handling script’s name).
To access the values passed to the page
in this way, turn to the $_GET variable.
Just as you would when using $_POST,
refer to the specific name as an index in
$_GET. In that example, page.php receives
a $_GET['var'] variable with a value of
value, a $_GET['age'] variable with a
value of 20, and so forth.
You can pass data to a PHP script in this
way by creating an HTML form that uses
the GET method. But you can also use this
same idea to send data to a PHP page
without the use of the form. Normally you’d
do so by creating links:

➝ Some Link

That link, which could be dynamically generated by PHP, will pass the value 22 to
page.php, accessible in $_GET['id'].
To try this for yourself, the next pair of
scripts will easily demonstrate this concept,
using a hard-coded HTML page.

68 Chapter 3

Script 3.6 This HTML page uses links to pass
values to a PHP script in the URL (thereby
emulating a form that uses the GET method).
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<!doctype html>

Greetings!

Click a link to say hello:

li>Michael
Celia
Jude
Sophie

</div>

To create the HTML page:
1. B
egin a new document in your text
editor or IDE, to be named hello.html
(Script 3.6):

A The simple HTML page, with four
links to the PHP script.

Greetings!

2. C
reate links to a PHP script, passing
values along in the URL:

Michael

Celia

Jude

Sophie

The premise here is that the user will
see a list of links, each associated with
a specific name A. When the user
clicks a link, that name is passed to
hello.php in the URL B.
continues on next page

B The HTML source of the page shows how values are being passed
along in the URL for the four links.

HTML Forms and PHP

If you want to use different names, that’s
fine, but stick to one-word names without
spaces or punctuation or else they won’t
be passed to the PHP script properly.
3. Complete the HTML page:

4. S
ave the script as hello.html, and
place it within the proper directory on
your PHP-enabled server.
5. L oad the HTML page through a URL in
your browser.
Although you can view HTML pages
without going through a URL, you’ll click
links in this page to access the PHP script,
so you’ll need to start off using a URL
here. Don’t click any of the links yet,
because the PHP script doesn’t exist!
To create the PHP script:
1. B
egin a new document in your text
editor or IDE, to be named hello.php
(Script 3.7):

Greetings!

70 Chapter 3
Script 3.7 This PHP page refers to the name value
passed in the URL in order to print a greeting.
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<!doctype html>

Greetings!

Hello, $name!";
?>

2. Begin the PHP code:
Hello, $name!";
The name variable is sent to the
page through the URL (see Script
3.6). To access that value, refer to
$_GET['name']. Again, you would use
$_GET (as opposed to $_POST) because
the value is coming from a GET request.
As with earlier PHP scripts, the value in
the predefined variable ($_GET) is first
assigned to another variable, to simplify
the syntax in the print statement.
5. C
omplete the PHP code and the HTML
page:
?>

6. S
ave the script as hello.php, and place
it within the proper directory on your
PHP-enabled server.
It should be saved in the same directory
as hello.html (Script 3.6).
7. C
lick the links in hello.html to view
the result C and D.
continues on next page
HTML Forms and PHP
71
If you run hello.php directly (that
is, without clicking any links), you’ll get an
error notice because no name value would be
passed along in the URL E.
Because hello.php reads a value from
the URL, it actually works independently of
hello.html. For example, you can directly
edit the hello.php URL to greet anyone,
even if hello.html does not have a link for
that name F.
If you want to use a link to send multiple
values to a script, separate the name=value
pairs (for example, first_name=Larry) with
the ampersand (&). So, another link may be
hello.php?first_name=Larry&last_
name=Ullman. You should continue to use
only single words, without punctuation or
spaces, however (until you later learn about
the urlencode() function).
Although the example here—setting the
value of a person’s name—may not be very
practical, this basic technique is useful on
many occasions. For example, a PHP script
might constitute a template, and the content
of the resulting web page would differ based
on the values the page received in the URL.
72
Chapter 3
E If the $_GET['name'] variable isn’t assigned
a value, the browser prints out this awkward
message, along with the error notice.
F Any value assigned to name (lowercase) in the
URL is used by the PHP script.
Review and Pursue
If you have any problems with the review
questions or the pursue prompts, turn
to the book’s supporting forum
(www.LarryUllman.com/forums/).
Review
n
n
n
n
n
What is the significance of a form’s
action attribute?
What is the significance of a form’s
method attribute? Is it more secure to
use GET or POST? Which method type
can be bookmarked in the browser?
hat predefined variable will contain
W
the data from a form submission? Note:
There are multiple answers.
hy must an HTML page that contains
W
a form that’s being submitted to a PHP
script be loaded through a URL?
nder what circumstances will attempts
U
to enable display_errors in a script
not succeed? Why is it less secure to
enable display_errors on live sites?
HTML Forms and PHP
73
Pursue
n
n
n
n
74
L oad feedback.html in your browser
without going through a URL (that is,
the address bar would likely start with
file://). Fill out and submit the form.
Observe the result so that you can
recognize this problem, and understand
its cause, in case you see similar results
in the future.
n
n
n
If you have not already, and if you
can, make sure that display_errors
is enabled on your development
environment.
If you have not already, and if you can,
make sure that error_reporting is
set to E_ALL on your development
environment (or E_ALL | E_STRICT in
earlier versions of PHP).
ry introducing different errors in a
T
PHP script—by improperly balancing
quotation marks, failing to use semicolons, referring to variables improperly,
and so on—to see the result.
Chapter 3
n
Experiment with the hello.html and
hello.php pages to send different
values, including numbers, to the PHP
script through the URL.
Create a variation on hello.html that
sends multiple name=value pairs to a
PHP script. Have the PHP script then
print all the received values.
If you are the inquisitive type and don’t
mind waiting for answers, try passing
more complicated values to a page
through the URL. Try using spaces and
punctuation to see what happens.
reate a new HTML form that performs
C
a task you envision yourself needing
(or a lighter-weight version of that functionality). Then create the PHP script
that handles the form, printing just the
received data.
4
Using
Numbers
Chapter 2, “Variables,” briefly discussed
the various types of variables, how to
assign values to them, and how they’re
generally used. In this chapter, you’ll work
specifically with number variables—both
integers (whole numbers) and floatingpoint numbers (aka floats or decimals).
You’ll begin by creating an HTML form that
will be used to generate number variables.
Then you’ll learn how to perform basic arithmetic, how to format numbers, and how to
cope with operator precedence. The last
two sections of this chapter cover incrementing and decrementing numbers, plus
generating random numbers. Throughout
the chapter, you’ll also learn about other
useful number-related PHP functions.
In This Chapter
Creating the Form
76
Performing Arithmetic
79
Formatting Numbers
83
Understanding Precedence
86
Incrementing and Decrementing
a Number
88
Creating Random Numbers
90
Review and Pursue
92
Creating the Form
Most of the PHP examples in this chapter
will perform various calculations based on
an e-commerce premise. A form will take
price, quantity, discount amount, tax rate,
and shipping cost A, and the PHP script
that handles the form will return a total
cost. That cost will also be broken down by
the number of payments the user wants to
make in order to generate a monthly cost
value B.
To start, let’s create an HTML page that
allows the user to enter the values.
A This form takes numbers from the user
and sends them to a PHP page.
To create the HTML form:
1. Begin a new HTML document in
your text editor or IDE, to be named
calculator.html (Script 4.1):

Product Cost Calculator
➝

Fill out this form to
➝ calculate the total cost:
2. Create the initial form tag:

This form tag begins the HTML form. Its
action attribute indicates that the form
data will be submitted to a page named
handle_calc.php. The tag’s method
attribute tells the page to use POST to
send the data. See Chapter 3, “HTML
Forms and PHP,” for more details on
choosing a method.
76
Chapter 4
B The PHP script performs a series of calculations
on the submitted data and outputs the results. The
results will look like this by the end of the chapter.
Script 4.1 This basic HTML form will provide the
numbers for various mathematical calculations
over multiple PHP scripts.
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Product Cost Calculator

Fill out this form to calculate
the total cost:

Price:
Quantity:
Discount:
Tax: (%)
Shipping method:
3. Create the inputs for the price, quantity,
discount, and tax:
Price:
Quantity:
Discount:
Tax: (%)
Although HTML5 does have a number
input type, it’s not always the right solution because it’s more naturally suited
to taking integer values. For that reason,
the quantity input will be a number type,
whereas the others will be text.
To guide the user, a parenthetical indicates that the tax should be entered as
a percent.
Remember that the names used for the
inputs should correspond to valid PHP
variable names: Use letters, numbers,
and the underscore only; don’t start with
a number; and so forth.
continues on next page
Number of payments to make:

Using Numbers
77
4. Add a field in which the user can select
a shipping method:
Shipping method:
The shipping selection is made using
a drop-down menu. The value of the
selected option is the cost for that
option. If the user selects, for example,
the Put a move on it. option, the value
of $_POST['shipping'] in handle_
calc.php will be 8.95.
5. Complete the HTML form:
Number of payments to make:
➝

The final two input types take a number
for how many payments are required
and then create a submit button (labeled
Calculate!). The closing form tag marks
the end of the form section of the page.
6. Complete the HTML page:

7. Save the script as calculator.html,
and view it in your browser.
Because this is an HTML page, you can
view it directly in a browser.
78
Chapter 4
Script 4.2 This PHP script performs all the
standard mathematical calculations using the
numbers submitted from the form.
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39

Product Cost Calculator</
title>
<style type="text/css">
.number { font-weight: bold; }
</style>
</head>
<body>
<?php // Script 4.2 - handle_calc.php
/* This script takes values from
calculator.html and performs
total cost and monthly payment
calculations. */
// Address error handling, if you want.
// Get the values from the $_POST array:
$price = $_POST['price'];
$quantity = $_POST['quantity'];
$discount = $_POST['discount'];
$tax = $_POST['tax'];
$shipping = $_POST['shipping'];
$payments = $_POST['payments'];

// Calculate the total:
$total = $price * $quantity;
$total = $total + $shipping;
$total = $total - $discount;

// Determine the tax rate:
$taxrate = $tax / 100;
$taxrate = $taxrate + 1;

// Factor in the tax rate:
$total = $total * $taxrate;

// Calculate the monthly payments:
$monthly = $total / $payments;

code continues on next page

Performing Arithmetic
Just as you learned in grade school, basic
mathematics involves the principles of
addition, subtraction, multiplication, and
division. These are performed in PHP using
the most obvious operators:
n

Addition (+)

Subtraction (-)

Multiplication (*)

Division (/)

To use these operators, you’ll create a PHP
script that calculates the total cost for the
sale of some widgets. This handling script
could be the basis of a shopping cart application—a very practical web page feature
(although in this case the relevant number
values will come from calculator.html).
When you’re writing this script, be sure to
note the comments (Script 4.2) used to
illuminate the different lines of code and
the reasoning behind them.

To create your sales cost calculator:
1. Create a new document in your
text editor or IDE, to be named
handle_calc.php (Script 4.2):
<!doctype html>
<html lang="en">
<head>

<title>Product Cost Calculator
➝

continues on next page
Using Numbers
79
The head of the document defines
one CSS class, named number. Any
element within the page that has that
class value will be given extra font
weight. In other words, when the numbers from the form, and the results of
the various calculations, are printed
in the script’s output, they’ll be made
more obvious.
2. Insert the PHP tag and address error
handling, if desired:
You have selected to
purchase:

$quantity widget(s) at

$$price
price each plus a

$$shipping shipping cost and a

$tax
percent tax rate.

After your $$discount
discount, the total cost is
$$total.

Divided over $payments
monthly payments, that would be
$$monthly each.";
?>

4. Begin calculating the total cost:
$total = $price * $quantity;
$total = $total + $shipping;
$total = $total - $discount;
The asterisk (*) indicates multiplication in
PHP, so the total is first calculated as the
number of items purchased ($quantity)
multiplied by the price. Then the shipping
cost is added to the total value (remember that the shipping cost correlates
to the value attribute of each shipping
drop-down menu’s option tags), and
the discount is subtracted.
Note that it’s perfectly acceptable to
determine a variable’s value in part by
using that variable’s existing value (as
is done in the last two lines).
5. Calculate the tax rate and the new total:
$taxrate = $tax / 100;
$taxrate = $taxrate + 1;
$total = $total * $taxrate;
The tax rate should be entered as a
percent—for example, 8 or 5.75. This
number is then divided by 100 to get
the decimal equivalent of the percent
(.08 or .0575). Finally, you calculate how
much something costs with tax by adding
1 to the percent and then multiplying
that new rate by the total. This is the
mathematical equivalent of multiplying
the decimal tax rate times the total and
then adding this result to the total (for
example, a 5 percent tax on $100 is
$5, making the total $105, which is the
same as multiplying $100 times 1.05).
6. Calculate the monthly payment:
$monthly = $total / $payments;
As an example of division, assume that
the widgets can be paid for over the
course of many months. Hence, you
divide the total by the number of payments to find the monthly payment.
7. Print the results:
print "You have selected to
➝ purchase:

$quantity
➝ widget(s) at

$$price
➝ price each plus a

$$shipping
➝ shipping cost and a

$tax
➝ percent tax rate.

After your $$discount
➝ discount, the total cost is
$$total
➝ .

Divided over $payments
➝ monthly payments, that would be
➝ $
➝ $monthly each.";
The print statement sends every value
to the browser along with some text.
To make it easier to read,
tags are
added to format the browser result; in
addition, the print function operates
over multiple lines to make the PHP
code cleaner. Each variable’s value will
be highlighted in the browser by wrapping it within span tags that have a class
attribute of number (see Step 1).
8. Close the PHP section, and complete
the HTML page:
?>

9. Save the script as handle_calc.php,
and place it in the proper directory for
your PHP-enabled server.
Make sure that calculator.html is in
the same directory.
continues on next page
Using Numbers
81
10. Test the script in your browser by filling
out A and submitting B the form.
Not to belabor the point, but make sure
you start by loading the HTML form
through a URL (http://something) so
that when it’s submitted, the PHP script
is also run through a URL.
You can experiment with these values
to see how effectively your calculator
works. If you omit any values, the resulting message will just be a little odd but
the calculations should still work C.
As you’ll certainly notice, the calculator
comes up with numbers that don’t correspond
well to real dollar values (see B and C). In
the next section, “Formatting Numbers,” you’ll
learn how to address this issue.
If you want to print the value of the total
before tax or before the discount (or both),
you can do so in two ways. You can insert the
appropriate print statements immediately
after the proper value has been determined
but before the $total variable has been
changed again. Or you can use new variables
to represent the values of the subsequent
calculations (for example, $total_with_tax
and $total_less_discount).
Attempting to print a dollar sign followed
by the value of a variable, such as $10 (where 10
comes from a variable), has to be handled carefully. You can’t use the syntax $$variable,
because the combination of two dollar signs
creates a type of variable that’s too complex
to discuss in this book. One solution is to put
something—a space or an HTML tag, as in this
example—between the dollar sign and the
variable name. Another option is to escape the
first dollar sign:
print "The total is \$$total";
A third option is to use concatenation, which is
introduced in the next chapter.
82
Chapter 4
A The HTML form…
B …and the resulting calculations.
C You can omit or change any value and rerun
the calculator. Here the tax and discount values
have been omitted.
This script performs differently, depending on whether the various fields are submitted.
The only truly problematic field is the number
of monthly payments: If this is omitted, you’ll
see a division-by-zero warning. Chapter 6,
“Control Structures,” will cover validating form
data before it’s used.
Formatting Numbers
Although the calculator is on its way to
being practical, it still has one legitimate
problem: You can’t ask someone to make
a monthly payment of $10.13183333! To
create more usable numbers, you need to
format them.
Two functions are appropriate for this
purpose. The first, round(), rounds a value
to a specified number of decimal places.
The function’s first argument is the number
to be rounded. This can be either a number
or a variable that has a numeric value. The
second argument is optional; it represents
the number of decimal places to which
to round. If omitted, the number will be
rounded to the nearest integer. For example:
round(4.30); // 4
round(4.289, 2); // 4.29
$num = 236.26985;
round($num); // 236
The other function you can use in this
situation is number_format(). It works like
round() in that it takes a number (or a variable with a numeric value) and an optional
decimal specifier. This function has the
added benefit of formatting the number
with commas, the way it would commonly
be written:
number_format(428.4959, 2); // 428.50
number_format(428, 2); // 428.00
number_format(1234567); // 1,234,567
Let’s rewrite the PHP script to format the
numbers appropriately.
Using Numbers
83
To format numbers:
1. Open handle_calc.php in your text
editor or IDE, if it is not already open
(Script 4.2).
2. After all the calculations but before the
print statement, add the following
(Script 4.3):
$total = number_format($total, 2);
$monthly = number_format
➝ ($monthly, 2);
To format these two numbers, apply
this function after every calculation has
been made but before they’re sent to
the browser. The second argument (the
2) indicates that the resulting number
should have exactly two decimal places;
this setting rounds the numbers and
adds zeros at the end, as necessary.
Script 4.3 The number_format() function is
applied to the values of two number variables, so
they are more appropriate to the example.
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Product Cost Calculator</
title>
<style type="text/css">
.number { font-weight: bold;}
</style>
</head>
<body>
<?php // Script 4.3 - handle_calc.php #2
/* This script takes values from
calculator.html and performs
total cost and monthly payment
calculations. */
// Address error handling, if you want.
// Get the values from the $_POST array:
$price = $_POST['price'];
$quantity = $_POST['quantity'];
$discount = $_POST['discount'];
$tax = $_POST['tax'];
$shipping = $_POST['shipping'];
$payments = $_POST['payments'];
// Calculate the total:
$total = $price * $quantity;
$total = $total + $shipping;
$total = $total - $discount;
// Determine the tax rate:
$taxrate = $tax/100;
$taxrate = $taxrate + 1;
// Factor in the tax rate:
$total = $total * $taxrate;
// Calculate the monthly payments:
$monthly = $total / $payments;
// Apply the proper formatting:
$total = number_format($total, 2);
$monthly = number_format($monthly, 2);

code continues on next page

84 Chapter 4

Script 4.3 continued
44
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51
52

53
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// Print out the results:
print "<p>You have selected to
purchase:<br>
<span class=\"number\">$quantity</span>
widget(s) at <br>
$<span class=\"number\">$price</span>
price each plus a <br>
$<span class=\"number\">$shipping</span>
shipping cost and a <br>
<span class=\"number\">$tax</span>
percent tax rate.<br>
After your $<span
class=\"number\">$discount</span>
discount, the total cost is
$<span class=\"number\">$total</
span>.<br>
Divided over <span
class=\"number\">$payments</span>
monthly payments, that would be $<span
class=\"number\">$monthly</span> each.</
p>";
?>
</body>
</html>

A Another form entry.

3. Save the file, place it in the same directory as calculator.html, and test it in
your browser A and B.
Another, much more complex way to
format numbers is to use the printf() and
sprintf() functions. Because of their tricky
syntax, they’re not discussed in this book; see
the PHP manual for more information.
Non-Windows versions of PHP also have
a money_format() function, which can be
used in lieu of number_format().
The round() function rounds exact
halves (.5, .05, .005, and so on) up, although
this behavior can be configured. See the PHP
manual for details.
In PHP, function calls can have spaces
between the function name and its parentheses
or not. Both of these are fine:

round ($num);
round($num);
The number_format() function takes two
other optional arguments that let you specify
what characters to use to indicate a decimal
point and break up thousands. This is useful,
for example, for cultures that write 1,000.89 as
1.000,89. See the PHP manual for the correct
syntax, if you want to use this option.

B The updated version of the script returns more
appropriate number values thanks to the number_

format() function.

Using Numbers

Understanding
Precedence
Inevitably, after a discussion of the various
sorts of mathematical operators comes the
discussion of precedence. Precedence
refers to the order in which a series of calculations are executed. For example, what
is the value of the following variable?
$number = 10 – 4 / 2;

Is $number worth 3 (10 minus 4 equals 6,
divided by 2 equals 3) or 8 (4 divided by
2 equals 2, subtracted from 10 equals 8)?
The answer here is 8, because division
takes precedence over subtraction.
Appendix B, “Resources and Next Steps,”
shows the complete list of operator
precedence for PHP (including operators
that haven’t been covered yet). However,
instead of attempting to memorize a large
table of peculiar characters, you forgo
any deliberation by using parentheses.
Parentheses always take precedence over
any other operator. Thus:
$number = (10 – 4) / 2; // 3
$number = 10 – (4 / 2); // 8

Using parentheses in your calculations
ensures that you never see peculiar results
due to precedence issues. Parentheses
can also be used to rewrite complex calculations in fewer lines of code. Let’s rewrite
the handle_calc.php script, combining
multiple lines into one by using parentheses,
while maintaining accuracy.

To manage precedence:
1. Open handle_calc.php in your text
editor or IDE, if it is not already open
(Script 4.3).

Chapter 4

Script 4.4 By using parentheses, calculations
made over multiple lines (compare with Script 4.3)
can be condensed without affecting the script’s
mathematical accuracy.
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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Product Cost Calculator</
title>
<style type="text/css">
.number { font-weight: bold;}
</style>
</head>
<body>
<?php // Script 4.4 - handle_calc.php #3
/* This script takes values from
calculator.html and performs
total cost and monthly payment
calculations. */
// Address error handling, if you want.
// Get the values from the $_POST array:
$price = $_POST['price'];
$quantity = $_POST['quantity'];
$discount = $_POST['discount'];
$tax = $_POST['tax'];
$shipping = $_POST['shipping'];
$payments = $_POST['payments'];
// Calculate the total:
$total = (($price * $quantity) +
$shipping) - $discount;

// Determine the tax rate:
$taxrate = ($tax / 100) + 1;

// Factor in the tax rate:
$total = $total * $taxrate;
// Calculate the monthly payments:
$monthly = $total / $payments;
// Apply the proper formatting:
$total = number_format ($total, 2);
$monthly = number_format ($monthly, 2);
code continues on next page

Script 4.4 continued
41
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47

48
49

50
51
52
53

2. Replace the three lines that initially calculate the order total with the following
(Script 4.4):
$total = (($price * $quantity) +
➝ $shipping) - $discount;

In this script, it’s fine to make all the
calculations in one step, as long as you
use parentheses to ensure that the
math works properly. The other option
is to memorize PHP’s rules of precedence for multiple operators, but using
parentheses is a lot easier.
3. Change the two lines that calculate and
add in the tax to this:
$taxrate = ($tax / 100) + 1;

Again, the tax calculations can be made
in one line instead of two separate ones.
4. Save the script, place it in the same
directory as calculator.html, and test
it in your browser A B.
Be sure that you match your parentheses
consistently as you create your formulas (every
opening parenthesis requires a closing parenthesis). Failure to do so will cause parse errors.
Granted, using the methods applied here,
you could combine all the total calculations
into just one line of code (instead of three)—
but there is such a thing as oversimplifying.

A Testing the form one more time.

B Even though the calculations have been

condensed, the math works out the same. If you
see different results or get an error message,
double-check your parentheses for balance (an
equal number of opening and closing parentheses).

Using Numbers

Incrementing and
Decrementing
a Number
PHP, like most programming languages,
includes shortcuts that let you avoid ugly
constructs such as
$tax = $tax + 1;

When you need to increase the value of
a variable by 1 (known as an incremental
adjustment) or decrease the value of a
variable by 1 (a decremental adjustment),
you can use ++ and --, respectively:
$var = 20;
$var++; //
$var++; //
$var--; //

// 20
21
22
21

Solely for the sake of testing this concept,
you’ll rewrite the handle_calc.php script
one last time.

To increment the value of a variable:
1. Open handle_calc.php in your text
editor or IDE, if it is not already open
(Script 4.4).
2. Change the tax rate calculation from
Script 4.3 to read as follows (Script 4.5):
$taxrate = $tax / 100;
$taxrate++;

The first line calculates the tax rate
as the $tax value divided by 100. The
second line increments this value by 1
so that it can be multiplied by the total
to determine the total with tax.
3. Save the script, place it in the same
directory as calculator.html, and test
it in your browser A B.

88 Chapter 4

Script 4.5 Incrementing or decrementing a
number is a common operation using ++ or ––,
respectively.
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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Product Cost Calculator</
title>
<style type="text/css">
.number { font-weight: bold;}
</style>
</head>
<body>
<?php // Script 4.3 - handle_calc.php #4
/* This script takes values from
calculator.html and performs
total cost and monthly payment
calculations. */
// Address error handling, if you want.
// Get the values from the $_POST array:
$price = $_POST['price'];
$quantity = $_POST['quantity'];
$discount = $_POST['discount'];
$tax = $_POST['tax'];
$shipping = $_POST['shipping'];
$payments = $_POST['payments'];
// Calculate the total:
$total = (($price * $quantity) +
$shipping) - $discount;
// Determine the tax rate:
$taxrate = $tax / 100;
$taxrate++;

Script 4.5 continued
42
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48

49
50

51
52
53
54

Although functionally it doesn’t matter
whether you code $taxrate = $taxrate +
1; or the abbreviated $taxrate++, the latter
method (using the increment operator) is more
professional and common.
In Chapter 6, you’ll see how the increment
operator is commonly used in conjunction
with loops.

Arithmetic Assignment
Operators
PHP also supports a combination of
mathematical and assignment operators.
These are +=, -=, *=, and /=. Each will
assign a value to a variable by performing a calculation on it. For example, these
next two lines both add 5 to a variable:
$num = $num + 5;
$num += 5;

This means the handle_calc.php script
could determine the tax rate using this:
$tax = $_POST['tax']; // Say, 5
$tax /= 100; // Now $tax is .05
$tax += 1; // 1.05

You’ll frequently see these shorthand
ways of performing arithmetic.

A The last execution of the form.

B It won’t affect your calculations if you use the
long or short version of incrementing a variable
(compare Scripts 4.4 and 4.5).

Using Numbers

Creating Random
Numbers
The last function you’ll learn about in this
chapter is mt_rand(), a random-number
generator. All it does is output a random
number:
$n = mt_rand(); // 31
$n = mt_rand(); // 87

The mt_rand() function can also take
minimum and maximum parameters, if you
prefer to limit the generated number to a
specific range:
$n = mt_rand(0, 10);

These values are inclusive, so in this case
0 and 10 are feasible returned values.
As an example of generating random
numbers, let’s create a simple “Lucky
Numbers” script.

To generate random numbers:
1. Begin a new document in your text
editor or IDE, to be named random.php
(Script 4.6):
<!doctype html>
<html lang="en">
<head>

<title>Lucky Numbers

2. Include the PHP tag and address error
management, if you need to:

Lucky Numbers

Your lucky numbers are:

$n1

$n2

$n3";
?>

3. Create three random numbers:
$n1 = mt_rand(1, 99);
$n2 = mt_rand(1, 99);
$n3 = mt_rand(1, 99);
A The three random numbers
created by invoking the
mt_rand() function.
This script prints out a person’s lucky
numbers, like those found on the back
of a fortune cookie. These numbers are
generated by calling the mt_rand()
function three separate times and assigning each result to a different variable.
4. Print out the numbers:
B Running the script again
produces different results.
print "Your lucky numbers
are:

$n1

$n2

$n3";
The print statement is fairly simple.
The numbers are printed, each on its
own line, by using the HTML break tag.
5. Close the PHP code and the HTML
page:
?>

6. Save the file as random.php, place it
in the proper directory for your PHPenabled server, and test it in your
browser A. Refresh the page to see
different numbers B.
The getrandmax() function returns the
largest possible random number that can be
created using mt_rand(). This value differs
by operating system.
PHP has other functions for generating
random numbers, such as random_int().
Unlike mt_rand(), random_init() creates
cryptographically secure random numbers.
Using Numbers
91
Review and Pursue
If you have any problems with the
review questions or the pursue prompts,
turn to the book’s supporting forum
(www.LarryUllman.com/forums/).
Review
n
n
What are the four primary arithmetic
operators?
Why will the following code not work:
print "The total is $$total";
What must be done instead?
n
n
n
n
n
Why must an HTML page that contains
a form that’s being submitted to a PHP
script be loaded through a URL?
What functions can be used to
format numerical values? How do you
format numbers to a specific number
of decimals?
What is the importance of operator
precedence?
What are the incremental and decremental operators?
What are the arithmetic assignment
operators?
Pursue
n
n
92
Look up the PHP manual page for one
of the new functions mentioned in this
chapter. Use the links on that page to
investigate a couple of other numberrelated functions that PHP has.
Create another HTML form for taking
numeric values. Then create the PHP
script that receives the form data,
performs some calculations, formats
the values, and prints the results.
Chapter 4
Other Mathematical Functions
PHP has a number of built-in functions
for manipulating mathematical data.
This chapter introduced round(),
number_format(), and mt_rand().
PHP has broken round() into two other
functions. The first, ceil(), rounds
every number to the next highest integer.
The second, floor(), rounds every
number to the next lowest integer.
Another function the calculator page
could make good use of is abs(), which
returns the absolute value of a number.
In case you don’t remember your absolute values, the function works like this:
$number = abs(-23); // 23
$number = abs(23); // 23
In layman’s terms, the absolute value of
a number is always a positive number.
Beyond these functions, PHP supports
all the trigonometry, exponent, base
conversion, and logarithm functions
you’ll ever need. See the PHP manual for
more information.
5
Using
Strings
As introduced in Chapter 2, “Variables,”
a second category of variables used by
PHP is strings—a collection of characters
enclosed within either single or double
quotation marks. The value of a string
variable may be a single letter, a word, a
sentence, a paragraph, HTML code, or even
a jumble of nonsensical letters, numbers,
and symbols (which might represent a
password). Strings may be the most common variable type used in PHP.
This chapter covers PHP’s most basic
built-in functions and operators for manipulating string data, regardless of whether
the string originates from a form or is first
declared within the script. Some common
techniques will be introduced: joining strings
together, trimming strings, and encoding
strings. Other uses for strings are illustrated
in subsequent chapters.
In This Chapter
Creating the HTML Form
94
Concatenating Strings
97
Handling Newlines
101
HTML and PHP
104
Encoding and Decoding Strings
108
Finding Substrings
113
Replacing Parts of a String
117
Review and Pursue
120
Creating the
HTML Form
As in Chapter 3, “HTML Forms and PHP,”
let’s begin by creating an HTML form that
sends different values—in the form of string
variables—to a PHP script. The theoretical
example being used is an online bulletin
board or forum where users can post a
message, their email address, and their
first and last names A.
To create the HTML form:
1. Begin a new HTML document in
your text editor or IDE, to be named
posting.html (Script 5.1):

Forum Posting

Please complete this form
➝ to submit your posting:
2. Create the initial form tag:

This form will send its data to the
handle_post.php script and will use
the POST method.
3. Add inputs for the first name, last name,
and email address:
First Name:
Last Name:
Email Address:
94
Chapter 5
A This HTML form is the basis for most
of the examples in this chapter.
Script 5.1 This form sends string data to a
PHP script.
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Forum Posting

Please complete this form to
submit your posting:

<p>First Name:
<p>Last Name:
The form uses two basic text input
types and one email type. Remember
that the various inputs’ name values
should adhere to the rules of PHP variable names (no spaces; must not begin
with a number; must consist only of
letters, numbers, and the underscore).
4. Add an input for the posting:
Posting: ➝
The posting field is a textarea, which
is a larger type of text input box.
5. Create a submit button, and close
the form:
<p>Email Address:

<p>Posting:
Every form must have a submit button
(or a submit image).
<input type="submit" name="submit"
value="Send My Posting">

6. Complete the HTML page:

continues on next page
Using Strings 95
7. Save the file as posting.html, place
it in the appropriate directory on your
PHP-enabled server, and view it in your
browser A.
This is an HTML page, so it doesn’t
have to be on a PHP-enabled server
in order for you to view it. But because
it will eventually send data to a PHP
script, it’s best to place the file on
your server.
Technically speaking, all form data, aside
from uploaded files, is sent to the handling
script as strings. This includes numeric data
entered into text boxes, options selected
from drop-down menus, checkbox or radio
button values, and so forth. Even the form in
Chapter 4, “Using Numbers,” sent strings with
numeric values to the handling script.
Many forum systems written in PHP
are freely available for your use. This book
doesn’t discuss how to fully develop one, but
a multilingual forum is developed in my PHP
and MySQL for Dynamic Web Sites (Fourth
Edition): Visual QuickPro Guide (Peachpit
Press, 2012).
This book’s website has a forum where
readers can post questions and other readers
(and the author) answer questions. You can
find it at www.LarryUllman.com/forums/.
96 Chapter 5
Concatenating Strings
Concatenation is an unwieldy term but a
useful concept. It refers to the appending
of one item onto another. Specifically, in
programming, you concatenate strings.
The period (.) is the operator for performing this action, and it’s used like so:
$s1 = 'Hello, ';
$s2 = 'world!';
$greeting = $s1 . $s2;
The result of this concatenation is that the
$greeting variable has a value of Hello,
world!
Because of the way PHP deals with
variables, the same effect could be
accomplished using
$greeting = "$s1$s2";
This code works because PHP replaces
variables within double quotation marks
with their value. However, the formal method
of using the period to concatenate strings is
more commonly used and is recommended
(it will be more obvious what’s occurring in
your code).
Another way of performing concatenation
involves the concatenation assignment
operator:
$greeting = 'Hello, ';
$greeting .= 'world!';
This second line roughly means “assign
to $greeting its current value plus the
concatenation of world!” The end result is
$greeting having the value Hello, world!
once again.
The posting.html script sends several
string variables to the handle_post.php
page. Of those variables, the first and last
names could logically be concatenated.
You’ll write the PHP script with this in mind.
Using Strings 97
To use concatenation:
1. Begin a new document in your
text editor or IDE, to be named
handle_post.php (Script 5.2):

Forum Posting

2. Create the initial PHP tag, and address
error management, if necessary:

Forum Posting

Thank you, $name, for your
posting:
$posting";
?>

4. Create a new $name variable using
concatenation:
$name = $first_name . ' ' .
$last_name;
This act of concatenation takes two
variables plus a space and joins them
all together to create a new variable,
named $name. Assuming that you
entered Elliott and Smith as the names,
$name would be equal to Elliott Smith.
5. Print out the message to the user:
print "Thank you, $name,
➝ for your posting:
$posting";
This message reports back to the user
what was entered in the form.
A The HTML form in use…
6. Close the PHP section and complete
the HTML page:
?>

B …and the resulting PHP page.
7. Save your script as handle_post.php,
place it in the same directory as
posting.html (on your PHP-enabled
server), and test both the form and the
script in your browser A B.
As a reminder, you must load the form
through a URL (http://something) so that,
when the form is submitted, the handling
PHP script is also run through a URL.
Using Strings 99
You can link as many strings as you
want using concatenation. You can even join
numbers to strings:
$new_string = $s1 . $s2 . $number;
This works because PHP is weakly typed,
meaning that its variables aren’t locked in to
one particular format. Here, the $number variable will be turned into a string and appended
to the value of the $new_string variable.
Concatenation can be used in many
ways, even when feeding arguments to a
function. An uncommon but functional
example would be
$text = nl2br($heading . $body);
The nl2br() function, first mentioned in
Chapter 1, “Getting Started with PHP,” will be
discussed in detail next.
If you used quotation marks of any kind
in your form and saw extraneous slashes in
the printed result, see the sidebar “Magic
Quotes” in Chapter 3 for an explanation of
the cause and for the fix. This is uncommon
in current versions of PHP.
As a reminder, it’s important to understand the difference between single and
double quotation marks in PHP. Characters
within single quotation marks are treated
literally; characters within double quotation
marks are interpreted (for example, a variable’s
name will be replaced by its value). See
Chapter 3 for a refresher.
Taking the first and last names as
separate inputs makes for a good concatenation example. However, not everyone has just
two names, and it’s best not to make such
assumptions in your own registration forms.
A more inclusive example would have a single
input for the user’s name.
100
Chapter 5
Handling Newlines
A common question beginning PHP developers have involves handling newlines
in strings. The textarea form element
allows a user to enter text over multiple
lines by pressing Return/Enter. Each use
of Return/Enter equates to a newline in
the resulting string. These newlines work
within a textarea but have no effect on a
rendered PHP page A B.
To create the equivalent of newlines in a
rendered web page, you use the break tag:

. Fortunately, PHP has the nl2br()
function, which automatically converts
newlines into break tags:
$var = nl2br($var);
A Newlines in form data like textareas…
Let’s apply this function to handle_post.php
so that the user’s posting retains its
formatting.
To convert newlines to breaks:
1. Open handle_post.php (Script 5.2)
in your text editor or IDE, if it is not
already open.
B …are not rendered by the browser.
continues on next page
Using Strings
101
2. Apply the nl2br() function when
assigning a value to the $posting
variable (Script 5.3):
$posting = nl2br($_POST
➝ ['posting'], false);
Now $posting will be assigned the
value of $_POST['posting'], with any
newlines converted to HTML break tags.
The second argument to the function—
the Boolean false—says that you do
not want XHTML-compliant break tags
created. In other words, the default
behavior is for this function to replace
newlines with
. In HTML5,

is more commonly used.
Script 5.3 When you use the nl2br() function,
newlines entered into the posting textarea are
honored when displayed in the browser.
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102
Chapter 5

Forum Posting

Thank you, $name, for your
posting:
$posting

"; ?> 3. Save the file, place it in the same directory as posting.html (on your PHP-enabled server), and test again in your browser C. Newlines can also be inserted into strings by placing the newline character—\n— between double quotation marks. C Now the same submitted data A is properly displayed over multiple lines in the browser. Other HTML tags, such as paragraph tags, also affect spacing in the rendered web page. You can turn newlines (or any character) into paragraph tags using a replacing function, but the code for doing so is far more involved than just invoking nl2br(). Newlines present in strings sent to the browser will have an effect, but only in the HTML source of the page D. D The HTML source, corresponding to B, shows the effect that newlines have in the browser (i.e., they add spacing within the HTML source code). Using Strings 103 HTML and PHP As stated several times over by now, PHP is a server-side technology that’s frequently used to send data to the browser. This data can be in the form of plain text, HTML code, or, more commonly, both. In this chapter’s primary example, data is entered in an HTML form and then printed back to the browser using PHP. A potential problem is that the user can enter HTML characters in the form, which can affect the resulting page’s formatting A B—or, worse, cause security problems. You can use a few PHP functions to manipulate HTML tags within PHP string variables: n n n htmlspecialchars() converts certain HTML tags into their entity versions. A If the user enters HTML code in the posting… htmlentities() turns all HTML tags into their entity versions. strip_tags() removes all HTML and PHP tags. The first two functions turn an HTML tag (for example, ) into an entity version like <span>. The entity version appears in the output but isn’t rendered. You might use either of these if you wanted to display code without enacting it. The third function, strip_tags(), removes HTML and PHP tags entirely. B …it’s rendered by the browser when reprinted. 104 Chapter 5 C Displaying HTML submitted by a user in a browser can have terrible consequences, such as the execution of JavaScript. You ought to watch for special tags in user-provided data for two reasons. First, as already mentioned, submitted HTML would likely affect the rendered page (for example, mess up a table, tweak the CSS, or just add formatting where there shouldn’t be any). The second concern is more important. Because JavaScript is placed within HTML script tags, a malicious user could submit JavaScript that would be executed when it’s redisplayed on the page C. This is how cross-site scripting (XSS) attacks are performed. To see the impact these functions have, this next rewrite of handle_post.php will use each of them and display the respective results. Using Strings 105 To address HTML in PHP: 1. Open handle_post.php (Script 5.3) in your text editor or IDE, if it is not already open. 2. Before the print line, add the following (Script 5.4): $html_post = htmlentities ➝ ($_POST['posting']); $strip_post = strip_tags ➝ ($_POST['posting']); To clarify the difference between how these two functions work, apply them both to the posting text, creating two new variables in the process. Refer to $_POST['posting'] here and not $posting because $posting already reflects the application of the nl2br() function, which means that break tags may have been introduced that were not explicitly entered by the user. 3. Alter the print statement to read as follows: print "

Thank you, $name, ➝ for your posting:

Original: $posting

Entity: $html_post

Stripped: $strip_post

➝

"; To highlight the different results, print out the three different versions of the posting text. First is the original posting as it was entered, after being run through nl2br(). Next is the htmlentities() version of the posting, which will show the HTML tags without rendering them. Finally, the strip_tags() version will be printed; it doesn’t include any HTML (or PHP) tags. 106 Chapter 5 Script 5.4 This version of the PHP script addresses HTML tags in two different ways. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 Forum Posting Thank you, $name, for your posting:

Original: $posting

Entity: $html_post

Stripped: $strip_post

"; ?> 4. Save the file, place it in the same directory as posting.html (on your PHP-enabled server), and test it again in your browser D E. If you view the HTML source code of the resulting PHP page F, you’ll also see the effect that applying these functions has. For security purposes, it’s almost always a good idea to use htmlentities(), htmlspecialchars(), or strip_tags() to any user-provided data that’s being printed to the browser. The only reason I don’t do so in this book is to minimize clutter. Today’s browsers can identify and block execution of potentially malicious JavaScript, although you should not rely on that behavior. D The HTML characters entered as part of a posting will now be addressed by PHP. The html_entity_decode() function does just the opposite of htmlentities(), turning HTML entities into their respective HTML code. Another useful function for outputting strings in the browser is wordwrap(). This function wraps a string to a certain number of characters. E The resulting PHP page shows the original post as it would look if printed without modification, the effect of htmlentities(), and the effect of strip_tags(). To turn newlines into breaks while still removing any HTML or PHP tags, apply nl2br() after strip_tags(): $posting = nl2br(strip_tags ➝ ($_POST['posting'])); In that line, the strip_tags() function will be called first, and its result will be sent to the nl2br() function. F The HTML source for the content displayed in E. Using Strings 107 Encoding and Decoding Strings At the end of Chapter 3, the section “Manually Sending Data to a Page” demonstrated how to use the thinking behind the GET form method to send data to a page. In that example, instead of using an actual form, data was appended to the URL, making it available to the receiving script. I was careful to say that only single words could be passed this way, without spaces or punctuation. But what if you want to pass several words as one variable value or use special characters? To safely pass any value to a PHP script through the URL, apply the urlencode() function. As its name implies, this function takes a string and encodes it (changes its format) so that it can properly be passed as part of a URL. Among other things, the function replaces spaces with plus signs (+) and translates special characters (for example, the apostrophe) into less problematic versions. You can use the function like so: $string = urlencode($string); To demonstrate one application of urlencode(), let’s update the handle_ post.php page so that it also creates a link that passes the user’s name and email address to a third page. 108 Chapter 5 Script 5.5 This script encodes two variables before adding them to a link. Then the values can be successfully passed to another page. 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Forum Posting Thank you, $name, for your posting:

$posting

Originally the array looks like this:
'; foreach ($grades as $student => $grade) { print "$student: $grade
\n"; } print '

After sorting the array by value using arsort(), the array looks like this:
'; foreach ($grades as $student => $grade) { print "$student: $grade
\n"; } print '

Originally the array ➝ looks like this:
'; foreach ($grades as $student => ➝ $grade) { print "$student: $grade
\n"; } print '

After sorting the array ➝ by value using arsort(), the ➝ array looks like this:
'; foreach ($grades as $student => ➝ $grade) { print "$student: $grade
\n"; } print '

After sorting the array by key using ksort(), the array looks like this:
'; foreach ($grades as $student => $grade) { print "$student: $grade
\n"; } print '

After sorting the array ➝ by key using ksort(), the array ➝ looks like this:
'; foreach ($grades as $student => ➝ $grade) { print "$student: $grade
\n"; } print '

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

Everything up until this comment will remain the same for every page in the web application. To indicate where the page-specific content begins (for your own benefit), include an HTML comment. When making a choice, err on the side of overcommenting your HTML and PHP code! Just before the comment, the siteContent area is begun. This area is defined in the CSS code and properly formats the main content part of the page. In other words, on every page, that page’s content will go within the one main that has a class of siteContent. 7. Mark the end of the changeable content: The code in Step 6 is the only text that will change on a page-by-page basis. Just as an HTML comment indicates where that section starts, one here indicates where it ends. 8. Add the footer: The footer includes a credit. 9. Finish the HTML page: 10. Save the file as template.html, and test it in your browser C. Once you’ve completed a prototype that you like, you can break it into its various parts to generate the template system. 6. Create the page’s content:

Welcome to a J.D. Salinger ➝ Fan Club

Lorem ipsum dolor sit ➝ amet...

For the prototype, the content is just a header and a whole lot of text (there’s more in the actual script than I’ve included in this step). Creating Web Applications 197 To create the header file: 1. Open template.html (Script 8.1) in your text editor or IDE, if it isn’t already open. 2. Select everything from the initial HTML code to the HTML comment D. Part of the benefit of identifying the start of the page-specific content with an HTML comment is that it simplifies breaking the model into its parts. D Using the prototype file, select and copy the initial lines of code to create the header. 198 Chapter 8 Script 8.2 This is a basic header file that creates the HTML head information, includes the CSS file, and begins the body. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Raise High the Roof Beam!

Raise High the Roof Beam!

3. Copy this code. Using your Edit menu or keyboard shortcut (Ctrl+C on Windows, Command+C on the Macintosh), copy all the highlighted code to your computer’s clipboard. 4. Create a new, blank document in your text editor or IDE, to be named header.html. 5. Paste the copied text into the document (Script 8.2). Using your Edit menu or keyboard shortcut (Ctrl+V on Windows, Command+V on the Macintosh), paste all the highlighted code into this new document. 6. Save the file as header.html. Now that the header file has been created, you’ll make the footer file using the same process.

Creating Web Applications 199 To create the footer file: 1. Open template.html (Script 8.1) in your text editor or IDE, if it isn’t already open. 2. Select everything from the HTML comment to the end of the script E. 3. Copy this code. 4. Create a new, blank document in your text editor, to be named footer.html. 5. Paste the copied text into the document (Script 8.3). Script 8.3 This is a basic footer file that concludes the HTML page. 1 2 3 4 5 6 7 8 9 10

6. Save the file as footer.html. There are many far more complex template systems you can use in PHP to separate the design from the logic. The best known of these is probably Smarty (www.smarty.net). E Again using the prototype file, select and copy the concluding lines of code for the footer. CSS Templates Cascading Style Sheets (CSS) have been an increasingly important part of the web for some time. Their initial usage was focused on cosmetics (font sizes, colors, and so on), but now CSS is commonly used, as in this chapter, to control the layout of pages. This example defines three areas of the page—header, main (i.e., content), and footer. The main area will change for each page. The other areas contain standard items, such as navigation links, that appear on each page of the site. Just to be clear: The relationship between PHP and CSS is the same as that between PHP and HTML—PHP runs on the server and HTML and CSS are significant to the browser. As with HTML, you can use PHP to generate CSS, but in this example, the CSS is hard-coded into a separate file. 200 Chapter 8 Using External Files As the preceding section stated, you can save development time by creating separate pages for particular elements and then incorporating them into the main PHP pages using specific functions. Two of these functions are include() and require(): include('file.php'); require('file.html'); Both functions work the same way, with one relatively key difference: If an include() function fails, the PHP script generates a warning A but continues to run. Conversely, if require() fails, it terminates the execution of the script B. Both include() and require() incorporate the referenced file into the main file (for clarity’s sake, the file that has the include() or require() line is the including or parent file). The result is the same as if the included code were part of the parent file in the first place. Understanding this basic idea is key to making the most of external files: Including a file makes it as if that file’s contents were in the parent script to begin with. This means that any code within the included file not within PHP tags is treated as HTML. And this is true regardless of what extension the included file has, because it’s the extension of the including file that counts. A When an include() fails, warnings are issued, but the script continues to execute. B When a require() function call fails, warnings and errors are issued and the script stops running. Creating Web Applications 201 There are many reasons to use included files. You could put your own defined functions into a common file (see Chapter 10, “Creating Functions,” for information on writing your own functions). You might also want to place your database access information into a configuration file. First, however, let’s include the template files created in the preceding section of the chapter in order to make pages abide by a consistent design. To use external files: 1. Create a new document in your text editor or IDE, to be named index.php. Script 8.4 Once the two included files have been created, the include() function incorporates them into the parent file to create the complete HTML page on the fly. 1 2 3 4 5 6 7 8 9 10 11 2. Start with the initial PHP tags, and add any comments (Script 8.4):

Welcome to a J.D. Salinger Fan Club!

12 13 14 include('templates/footer.html'); // Include the footer. File Navigation and Site Structure To be able to use external files, you need to understand file navigation on your computer or server. Just as you must correctly refer to other pages in HTML links or images in websites, you must properly point a parent file to the included scripts. You can do this by using absolute or relative paths. An absolute path is a complete, specific address, like the following: include('C:\inetpub\wwwfiles\ ➝ file.php'); include('/Users/larry/Sites/ ➝ file.php'); As long as the included file isn’t moved, an absolute path will always work. A relative path indicates where the included file is in relation to the parent file. These examples assume both are within the same directory: include('file.php'); include('./file.php'); The included file can also be in a directory below the parent one, as in this chapter’s example (also see C): include('templates/header.html'); Or, the included file could be in the directory above the parent: include('../file.php'); Finally, a note on site structure: Once you divvy up your web application into multiple pieces, you should begin thinking about arranging the files in appropriate folders. Complex sites might have the main folder, another for images, one for administration files, and a special directory for templates and included files. As long as you properly reference the files in your include() or require() statement, structuring your applications will work fine and give the added benefit of making them easier to maintain. 4. Include the header file: include('templates/header.html'); To use the template system, you include the header file here by invoking the include() function. Because the header file contains only HTML, all of its contents will be immediately sent to the browser as if they were part of this file. This line uses a relative path to refer to the included file (see the “File Navigation and Site Structure” sidebar) and assumes that the file is stored in the templates directory. 5. Close the PHP section, and create the page-specific content: ?>

Welcome to a J.D. Salinger ➝ Fan Club

Lorem ipsum dolor sit ➝ amet...

Because the bulk of this page is standard HTML, it’s easier to just exit out of the PHP section and then add the HTML rather than using print to send it to the browser. Again, there’s more blather in the actual script than I’ve included here. 6. Create another PHP section, and include the footer file: To finish the page, you need to include the footer file, which displays the footer and closes the HTML code. To do this, you create a new section of PHP—you can have multiple sections of PHP code within a script—and call the include() function again. continues on next page Creating Web Applications 203 7. Save the file as index.php. 8. Create a folder named templates within the main web document directory on your PHP-enabled computer or server. To further separate the design elements from the main content, the header and footer files go within their own directory. 9. Place header.html and footer.html in the templates directory you just created. 10. Place index.php in the same directory as the templates folder. The relative locations on the computer between the index page and the two HTML pages must be correct in order for the code to work. The two HTML pages go within the templates folder, and the templates folder and index.php are in the same folder (such as the web root directory). 11. Create a folder named css within the main web document directory on your PHP-enabled computer or server. The CSS scripts will need to go in this directory. 204 Chapter 8 web root index.php header.html templates footer.html concise.min.css css masthead.css C How the files and folders should be organized on your PHP-enabled server. 12. Place the concise.min.css and masthead.css scripts, available as part of the book’s downloadable code, in the css directory C. Even though the header file includes the CSS scripts, the reference to that script must be relative to index.php. It’s that page, after all, that will include header.html. 13. Run index.php in your browser D. The resulting page should look exactly like the original layout (C in the previous section of the chapter). 14. View the page’s source code in your browser. The source code should be exactly like the source code of the template.html script (Script 8.1), aside from the added comments for the script names and numbers. D This page has been dynamically generated using included files. Creating Web Applications 205 All three files in this template system— header.html, footer.html, and index.php —must use the same encoding in order to avoid problems (see Chapter 1, “Getting Started with PHP,” for more on encoding). Each file’s encoding must also match the encoding established in the HTML code. The require() and include() functions can be used with or without parentheses: require 'filename.html'; You might sometimes use a variable that stores the name of the file to be included: require $filename; Both include() and require() have variations: include_once() and require_once(). Each is identical to its counterpart except that it ensures that the same file can be included only one time (in a parent script). You should generally avoid using these, because they’ll adversely affect the script’s performance. If a section of PHP executes only a single command, it’s common to place both it and the PHP tags on a single line: If you see error messages like those in A and B, the parent script can’t locate an included file. This problem is most likely caused by a misspelled included filename or an error in the path (for example, using header.html instead of templates/header.html). 206 Chapter 8 If the rendered page does not seem to be reflecting the CSS styling, the HTML page can’t find the corresponding file. Make sure you’ve stored the file in the proper folder, with the correct name, and that the reference is correct relative to index.php. A file’s extension is less important for included files because they aren’t intended to be run directly. As a general rule of thumb, you’ll be safe using .html for an included file containing only or mostly HTML (in which case the extension indicates it’s an HTML-related file) and .php for included files containing only or mostly PHP. Some programmers use an .inc extension (for include), but security risks can arise with this practice. For that reason, use the .php extension for any file containing sensitive information (like database access parameters). And, of course, always use the .php extension for any PHP script that will be executed directly. Another good use of an external file is to place your error settings code there so that those changes are applied to every page in the website. The final closing PHP tag is not required, and many developers advocate omitting it because it’s unnecessary and the script may run faster without it. Using Constants Many of PHP’s data types have already been discussed in this book, primarily: numbers, strings, and arrays. Constants are another data type, but unlike variables, their values cannot change. Whereas variables are assigned values via the assignment operator (=), constants are assigned values using the define() function: define('CONSTANT_NAME', value); Notice that—as a rule of thumb—constants are named using all capital letters, although doing so isn’t required. Most important, constants don’t use the initial dollar sign as variables do, because constants are not variables. Here are two constants: define('PI', 3.14); define('CURRENCY', 'euros'); As with any value, quote those that are strings, not those that are numbers. Referring to constants is generally straightforward: print CURRENCY; number_format(PI, 1); But using constants within quotation marks is more complicated. You can’t print constants within single or double quotation marks, like this A: print "The cost is 468 CURRENCY"; print 'The cost is 468 CURRENCY'; Instead, concatenation or multiple print statements are required: print 'The cost is 468 ' . CURRENCY; or print 'The cost is 468 '; print CURRENCY; Along with the define() function for creating constants is the defined() function (note the final “d”). This function returns TRUE if the submitted constant has been defined. It’s often used as the basis for a conditional: if (defined('CONSTANT_NAME')) { ... As an example of working with constants, you’ll give the sample application the ability to display a different title (which appears at the top of the browser window) for each page. To accomplish this, you’ll define a constant in the parent script that will then be printed by the header file. This technique works because any variables or constants that exist in the parent document before the include() or require() call are available to the included file (it’s as if the included file were part of the parent file). A The value of a constant cannot be printed using the constant’s name within quotation marks. Creating Web Applications 207 To use constants: 1. Create a new PHP document in your text editor or IDE, to be named books.php (Script 8.5):

J.D. Salinger's Books

The Catcher in the Rye
Nine Stories
Franny and Zooey
Raise High the Roof Beam, ➝ Carpenters and Seymour: An ➝ Introduction

The content here is simple but serves the page’s purpose nicely. 5. Create a new PHP section that includes the footer file: 208 Chapter 8 9 10 11 12 13 14 15 16 17 18 19 // Leave the PHP section to display lots of HTML: ?>

J.D. Salinger's Books

The Catcher in the Rye
Nine Stories
Franny and Zooey
Raise High the Roof Beam, Carpenters and Seymour: An Introduction

Script 8.6 The header.html file is modified so that it can set the page title value based on the existence and value of a constant. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 <?php // Print the page title. if (defined('TITLE')) { // Is the title defined? print TITLE; } else { // The title is not defined. print 'Raise High the Roof Beam! A J.D. Salinger Fan Club'; } ?>

Raise High the Roof Beam!

Books
Stories
Quotes
Login
Register

8. If you want, add the constant definition line to index.php to change its title. The formal rules for naming constants are exactly like those for variables except for the omission of a dollar sign. Constant names must begin with a letter or an underscore; can contain any combination of letters, numbers, and the underscore; and are case-sensitive. PHP runs with several predefined constants. These include PHP_VERSION (the version of PHP running) and PHP_OS (the operating system of the server). B The books page uses a PHP constant to create its title. In Chapter 9, “Cookies and Sessions,” you’ll learn about another constant, SID (which stands for session ID). An added benefit of using constants is that they’re global in scope. This concept will mean more to you after you read the section “Understanding Variable Scope” in Chapter 10. Not only can the value of a constant never be changed, a constant can’t be deleted (unset, technically). As of PHP 5.6, a constant can contain an array of values. In earlier versions of the language, a constant was scalar: it could store only a single value. 210 Chapter 8 C Because the index page didn’t have a TITLE constant defined in it, the default page title is used (thanks to the conditional in Script 8.6). Working with the Date and Time that can be. The basic usage of the date() function is just PHP has a few functions for working with the date and time, the most important of which is date(). The only thing the date() function does is return date and time information in a format based on the arguments it’s fed, but you’d be surprised how useful A long list of possible options is available for formatting, as indicated in Table 8.1 (the PHP manual lists a few more). These parameters can also be combined—for example, date('l F j, Y') returns Thursday January 26, 2017. date('formatting'); TABLE 8.1 Date() Function Formatting Character Meaning Example Y Year as 4 digits 2017 y Year as 2 digits 17 L Is it a leap year? 1 (for yes) n Month as 1 or 2 digits 2 m Month as 2 digits 02 F Month February M Month as 3 letters Feb j Day of the month as 1 or 2 digits 8 d Day of the month as 2 digits 08 l (lowercase L) Day of the week Monday D Day of the week as 3 letters Mon w Day of the week as a single digit 0 (Sunday) z Day of the year: 0 to 365 189 t Number of days in the month 31 S English ordinal suffix for a day, as 2 characters rd g Hour; 12-hour format as 1 or 2 digits 6 G Hour; 24-hour format as 1 or 2 digits 18 h Hour; 12-hour format as 2 digits 06 H Hour; 24-hour format as 2 digits 18 i Minutes 45 s Seconds 18 u Microseconds 1234 a am or pm am A AM or PM PM U Seconds since the epoch 1048623008 e Time zone UTC I (capital i) Is it daylight savings? 1 (for yes) O Difference from GMT +0600 Creating Web Applications 211 The date() function can take a second argument, named a timestamp. A timestamp is a number representing how many seconds have passed since midnight on January 1, 1970—a moment known as the epoch. Finally, realize that at least three time zones are involved, then: The time() function returns the timestamp for the current moment. The mktime() function can return a timestamp for a particular time and date: mktime(hour, minute, second, month, ➝ day, year); So the code $ts = mktime(12, 30, 0, 11, 5, ➝ 2016); assigns to $ts the number of seconds from the epoch to 12:30 on November 5, 2016. That number can then be fed into the date() function like so: date('D', $ts); This returns Sat, which is the three-letter format for that day of the week. An important thing to understand is that timestamps and the epoch use Universal Coordinated Time (curiously abbreviated UTC), which is equivalent to Greenwich Mean Time (GMT). As of PHP 5.1, you should establish the server’s time zone prior to calling any dateor time-related function. To do so, use date_default_timezone_set(timezone); The timezone value is a string like America/New_York or Pacific/Auckland. There are too many to list here (Africa alone has over 50), but see the PHP manual for them all. If you don’t take this step, you might see errors about a date or time function used without the time zone being set. 212 Chapter 8 n UTC n The server’s time zone n The time zone of the user Because PHP is a server-side technology, these functions reflect either UTC or the date and time on the server. To get the time on the client (in other words, on the computer where the browser viewing the page is located), you must use JavaScript. To demonstrate the date() function, let’s update the footer file so that it shows the current date and time in the sidebar A. It’s a trivial use of the function but will get you started sufficiently. To use date(): 1. Open footer.html (Script 8.3) in your text editor or IDE. 2. After the Concise CSS Framework mention, add the following (Script 8.7):

5. Close the PHP section, and finish the HTML code: ?>

6. Save the file as footer.html, place it in the templates directory of your PHP-enabled server, and test it in your browser A. The server’s time zone can also be set in the PHP configuration file (see Appendix A, “Installation and Configuration”). Establishing the time zone there is generally a better idea than doing so on a script-by-script basis. Added to PHP 5.3 are new ways to create and manipulate dates and times using the DateTime class. While useful, this new tool requires familiarity with object-oriented programming, therefore making it beyond the scope of this beginner’s book. Creating Web Applications 213 Handling HTML Forms with PHP, Revisited All the examples in this book so far have used two separate scripts for handling HTML forms: one that displayed the form and another that received and processed the form’s data. There’s certainly nothing wrong with this method, but coding the entire process in one script has its advantages. To make a page both display and handle a form, use a conditional A. if (/* form has been submitted */) { // Handle the form. } else { // Display the form. } There are many ways to determine if a form has been submitted. One option is to check whether any of the form’s variables are set: if (isset($_POST['something'])) { ... However, if the user submitted the form without completing it, that variable may not be set (depending on the corresponding form element type). A more reliable solution is to add a hidden input to a form so that it can be checked: 214 Chapter 8 Script A This flowchart represents how the same PHP script can both display and handle an HTML form. Again, the only purpose of this hidden input is to reliably indicate that the form has been submitted, even if the user did nothing to complete the form. To check for that, the handling PHP code would use this conditional: is the standard request made of most web pages. When the form is submitted, and its action attribute points to the same page, a second request of the script will be made, this time a POST request (assuming the form uses the POST method). With this in mind, you can test for a form’s submission by checking the request type, found in the $_SERVER array: if (isset($_POST['submitted'])) { ... Another way of checking for a form’s submission is to examine how the page was accessed. When you have a form that will be submitted back to the same page, two different types of requests will be made of that script B. The first request, which loads the form, will be a GET request. This if ($_SERVER['REQUEST_METHOD'] == ➝ 'POST') { ... As an example of this, you’ll create the basics of a login form. Script B When the same PHP script both displays and handles an HTML form, the script will be requested using two different methods. Creating Web Applications 215 To use one page to display and handle a form: 1. Begin a new PHP document in your text editor or IDE, to be named login.php (Script 8.8): Login Form

Users who are logged in ➝ can take advantage of certain ➝ features like this, that, and ➝ the other thing.

'; This text, which appears outside the main conditional, will always show in the browser, whether the form is being displayed or has been submitted. Because the core of this script revolves around a PHP conditional, it’s arguably clearer to print out HTML from PHP rather than exit out of the PHP code as you did in the previous two examples (index.php and books.php). 4. Begin the conditional to check whether the form has been submitted: Script 8.8 The login page serves two purposes: It displays the login form and handles its submission. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Login Form

Users who are logged in can take advantage of certain features like this, that, and the other thing.

'; // Check if the form has been submitted: if ($_SERVER['REQUEST_METHOD'] == 'POST') { Handle the form: // ( (!empty($_POST['email'])) && if (!empty($_POST['password'])) ) { 17 18 if ( (strtolower($_ POST['email']) == 'me@example. com') && ($_POST['password'] == 'testpass') ) { // Correct! 19 20 print '

You are logged in!
Now you can blah, blah, blah...

'; 21 22 23 24 } else { // Incorrect! print '

The submitted email address and password do not match those on file!
Go back and try again.

'; if ($_SERVER['REQUEST_METHOD'] == ➝ 'POST') { To test whether the form has been submitted, check whether $_SERVER['REQUEST_METHOD'] equals POST (case-sensitive). 25 26 27 28 29 } } else { // Forgot a field. code continues on next page 216 Chapter 8 Script 8.8 continued 30 print '

Please make sure you enter both an email address and a password!
Go back and try again.

'; 31 32 33 34 35 36 } } else { // Display the form. print ''; 37 38 39 40 41 42 43 44 45 } include('templates/footer.html'); // Need the footer. ?> 5. Create a nested pair of conditionals to process the form data: if ( (!empty($_POST['email'])) && (!empty($_POST['password'])) ) { if ( (strtolower ➝ ($_POST['email']) == ➝ 'me@example.com') && ➝ ($_POST['password'] == ➝ 'testpass') ) { // Correct! print '

You are logged ➝ in!
Now you can blah, ➝ blah, blah...

'; } else { // Incorrect! print '

The submitted email ➝ address and password do not ➝ match those on file!
Go ➝ back and try again.

'; } } else { // Forgot a field. print '

Please make sure you ➝ enter both an email address ➝ and a password!
Go back ➝ and try again.

'; } These conditionals handle the form data. The first conditional checks that both the email address and password variables have values. If they don’t, a message is displayed (Please make sure…). Within that first conditional, another conditional checks whether the email address is equal to me@example.com and the password is equal to testpass. If so, let’s say the user is logged in (it would be too advanced at this juncture to store and retrieve user information to create a real login system). Otherwise, a message indicates that the wrong values were entered. Creating Web Applications 217 Be certain to use the equals operator (==) here and not the assignment operator (=) in this conditional, which is a common mistake. Also, in case users enter their address as Me@example.com, or any other capitalized permutation, the strtolower() function is first applied to the email address, prior to checking for equality. Finally, some Concise CSS Framework classes are used to add styling—green and red coloring—to the printed text. 6. Complete the main conditional: } else { // Display the form. print ''; } This concludes the main conditional, which checks whether the form has been submitted. If the form hasn’t been submitted, then the form is displayed. The form itself is very simple C. To clarify a point of possible confusion, even though the form’s method attribute has a value of post (all lowercase), to check for the form’s submission the request method value is still POST (all uppercase). 218 Chapter 8 C This simple login page takes an email address and a password. 7. Require the footer file, and complete the PHP page: include('templates/footer.html'); ?> message. 8. Save the file as login.php, place it in the same directory as index.php, and test it in your browser D, E, and F. E Failure to submit either an email address or a This trick of checking for the presence of a hidden input can be confusing. It works because the same script—login.php—will be accessed twice by the user. The first time the form will not have been submitted, so a conditional checking if $_POST['submitted'] is set will be FALSE and the form will be displayed. Then the page will be accessed again after the user clicks submit, at which point the conditional becomes TRUE. D Upon successfully logging in, the user sees this password results in this message. F If either the email address or the password doesn’t match that in the script, the user sees this error message. If you want a page to handle a form and then immediately display the form again, use this: if ($_SERVER['REQUEST_METHOD'] == ➝ 'POST') { // Handle the form. } // Display the form. Creating Web Applications 219 Making Forms Sticky A sticky form remembers values entered into it. A common example is a search engine, which often displays your terms in the search box, even when showing the results of the search. You might also want to use sticky forms on occasions where the user failed to complete a form accurately and therefore must resubmit it A. From a technological standpoint, sticky forms work by having their form element values predetermined. You can make this happen by setting the value attribute of text inputs: A Creating sticky forms makes it easier for users to correct omissions in incomplete form submissions. To have PHP preset that value, print the appropriate variable between the quotation marks: The first time the form is run, the PHP code prints nothing (because the variable has no value). If the form is displayed again after submission, a value that the user originally entered in the form input will be displayed there automatically. That’s the basic idea, but a more professional implementation would address two things. B The HTML source of the page shows the PHP error caused by referring to a variable that does not exist. 220 Chapter 8 First, it’s best not to refer to variables that don’t exist. Doing so creates PHP warnings, and with the PHP code buried in a form element’s attribute, the warning itself will only be fully visible in the HTML source code B. To avoid that, check that the variable is set before printing it: C The registration form as the user first sees it. Second, certain characters that could be in a submitted value will cause problems if printed as a form element’s value. To prevent such problems, apply the htmlspecialchars() function (discussed in Chapter 5, “Using Strings”). With this in mind, a longer but better version of this code is as follows: To demonstrate this concept, you’ll create the shell of a registration form C. Creating Web Applications 221 To make a sticky form: 1. Create a new PHP script in your text editor or IDE, to be named register.php (Script 8.9): Registration Form

'; 4. Check whether the form has been submitted: if ($_SERVER['REQUEST_METHOD'] == ➝ 'POST') { Like the login page, this one script both displays and handles the registration form. To check whether the form has been submitted, the same code previously explained is used here. 5. Create a flag variable: $problem = false; The $problem variable will be used to indicate whether a problem occurred. Specifically, you want to make sure that every form input has been filled out before you formally register the user. Initially, this variable is set to FALSE, because no problems have occurred. This is the same approach used in Chapter 6, “Control Structures.” Script 8.9 The registration form uses a sticky feature so that it recalls the values previously entered into it. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Registration Form

Register so that you can take advantage of certain features like this, that, and the other thing.'; // Check if the form has been submitted: if ($_SERVER['REQUEST_METHOD'] == 'POST') { $problem = false; // No problems so far. Check for each value... // if (empty($_POST['first_name'])) { $problem = true; print '

Please enter your first name!

'; } if (empty($_POST['last_name'])) { $problem = true; print '

Please enter your last name!

'; } if (empty($_POST['email'])) { $problem = true; print '

Please enter your email address!

'; } code continues on next page 222 Chapter 8 6. Check that a first name was entered: Script 8.9 continued 33 34 35 36 37 38 39 40 41 42 43 if (empty($_POST['password1'])) { $problem = true; print '

Please enter a password!

'; } ($_POST['password1'] != $_ if POST['password2']) { $problem = true; print '

Your password did not match your confirmed password!

'; } (!$problem) { // If there weren't if any problems... 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 Print a message: // print '

You are now registered!
Okay, you are not really registered but...

'; Clear the posted values: // $_POST = []; } else { // Forgot a field. print '

Please try again!

'; } } // End of handle form IF. // Create the form: ?>

First Name:

if (empty($_POST['first_name'])) { $problem = true; print '

Please enter your ➝ first name!

'; } As a simple test to determine whether the user has entered a first name value, check that the variable isn’t empty. (This technique was first discussed in Chapter 6.) If the variable is empty, then indicate a problem by setting that variable to TRUE and print an error message. The error message has a class type of text--error, so that the CSS formatting is applied. (That class is defined within the Concise CSS Framework.) 7. Repeat the validation for the last name and email address: if (empty($_POST['last_name'])) { $problem = true; print '

Please enter your last ➝ name!

'; } if (empty($_POST['email'])) { $problem = true; print '

Please enter your ➝ email address!

'; } Both of these checks are variations on the username validation routine. continues on next page 64 code continues on next page Creating Web Applications 223 8. Validate the passwords: if (empty($_POST['password1'])) { $problem = true; print '

Please enter a ➝ password!

'; } if ($_POST['password1'] != $_ POST['password2']) { $problem = true; print '

Your password did ➝ not match your confirmed ➝ password!

'; } The password validation requires two conditionals. The first checks whether the $_POST['password1'] variable is empty. The second checks whether the $_POST['password1'] variable isn’t equal to the $_POST['password2'] variable. You don’t need to see if $_POST['password2'] is empty because if it is and $_POST['password1'] isn’t, the second conditional will catch that problem. If $_POST['password1'] and $_POST['password2'] are both empty, the first conditional will catch the mistake. 9. Check whether a problem occurred: if (!$problem) { print '

You are now ➝ registered!
Okay, you ➝ are not really registered ➝ but...

'; $_POST = []; If there were no problems, the $problem variable is still FALSE, and the initial condition here is TRUE (the condition is that $problem has a value of FALSE). In that case, the registration 224 Chapter 8 Script 8.9 continued 65

Last Name:

66 67

Email Address:

68 69 70 71 72 73 74 75 76

Password:

Confirm Password:

process would take place. The formal registration process, where the data is stored in a file or database, has not yet been developed, so a simple message appears in its stead here. Next, the $_POST variable is assigned the value of an empty array using the short array syntax. This line has the effect of wiping out the contents of the $_POST variable (i.e., resetting it as an empty array). This step is taken only upon a successful (theoretical) registration so that the values are not redisplayed in the registration form (e.g., see Step 12). 10. Complete the conditionals: } else { // Forgot a field. print '

Please try again! ➝

'; } } // End of handle form IF. The else clause applies if a problem occurred, in which case the user is asked to complete the form again. 11. Begin the HTML form: ?>

Unlike the login example, this page always displays the form. Therefore, the form isn’t part of any conditional. Also, because there’s a lot of HTML to be generated, it’ll be easier to leave the PHP section of the page and just output the HTML directly. 12. Create the sticky first name input:

➝ First Name:

To make the first name input sticky, preset its value attribute by printing out the $_POST['first_name'] variable, but only if it’s set. The conditional is therefore put within PHP tags within the HTML’s value section of the form element. As already mentioned, the htmlspecialchars() function is used to handle any potentially problematic characters. Note that if the user filled out the form properly, the entire $_POST array will have been reset, making this PHP conditional FALSE. If it helps your comprehension, write out the PHP code:

➝ First Name:

continues on next page Creating Web Applications 225 13. Repeat the process for the last name and email address:

➝ Last Name: ➝

Email ➝ Address:

These are variations on Step 12, switching the variable names as appropriate. 14. Add the rest of the form:

➝ Password: ➝

➝ Confirm Password: ➝ ➝

226 Chapter 8 D The registration form indicates any problems and retains the form values. E The registration form after the user successfully fills it out. It used to be the case that you couldn’t preset a value for a password input, but most browsers now support this feature. Then there is the submit button and the closing form tag. 15. Complete the PHP page: The last step is to include the HTML footer. 16. Save the file as register.php, place it in the proper directory on your PHPenabled server, and test it in your browser D and E. To preselect a pull-down menu, use selected="selected": Again, you’d need to use a PHP conditional to see if that text should be added to the element’s definition. To preset the value of a text area, place the value between the textarea tags: You should quote all attribute values in form inputs. If you don’t quote your values, any spaces in them mark the end of the value (for example, Larry Ullman will display as just Larry in the form input). To preset the status of radio buttons or checkboxes as selected, add the code checked="checked" to the input tag: Of course, you’d need to use a PHP conditional to see if that text should be added to the element’s definition. Creating Web Applications 227 Sending Email Sending email using PHP is theoretically simple, merely requiring only PHP’s mail() function. This function uses the server’s email application (such as sendmail on Unix or Mac OS X) or an SMTP (Simple Mail Transfer Protocol) server to send out the messages. The basic usage of this function is as follows: mail(to, subject, body); The first argument is the email address (or addresses, separated by commas) to which the email should be sent. The second argument establishes the message’s subject line, and the third argument creates the message’s content. This function can take another argument through which you can add more details (additional headers) to the email, including a From address, email priority, and carboncopy (CC) addresses: mail('someone@example.com', 'Test ➝ Email', 'This is a test email', ➝ 'From: 'email@example.com'); Although doing so is easy in theory, using this function in real-world code can be far more complex. For starters, setting up your own computer to send out email can be a challenge (see the sidebar “Configuring Your Server to Send Email”). Second, you should take steps to prevent malicious people from using your forms to send out spam. In our next example, an email will be sent to the provided email address. If a conniving user supplies multiple addresses A, an email will be sent to each one. You can safeguard against this in many ways. For the level of this book, one simple option is to confirm that there’s only a single @ present in the provided address (i.e., it’s only one email address). 228 Chapter 8 A A user could easily attempt to send emails to multiple recipients through a form like this. Script 8.10 In PHP, you can send email by calling the mail() function. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Registration Form

'; // Check if the form has been submitted: if ($_SERVER['REQUEST_METHOD'] == 'POST') { $problem = false; // No problems so far. Check for each value... // if (empty($_POST['first_name'])) { $problem = true; print '

Please enter your first name!

'; } if (empty($_POST['last_name'])) { $problem = true; print '

Please enter your last name!

'; } code continues on next page Script 8.10 continued 28 if (empty($_POST['email']) || (substr_count($_POST['email'], '@') != 1) ) { 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 $problem = true; print '

Please enter your email address!

'; } if (empty($_POST['password1'])) { $problem = true; print '

Please enter a password!

'; } ($_POST['password1'] != $_ if POST['password2']) { $problem = true; print '

Your password did not match your confirmed password!

'; } (!$problem) { // If there weren't if any problems... Print a message: // print '

You are now registered!
Okay, you are not really registered but...

'; Send the email: // $body = "Thank you, {$_ POST['first_name']}, for registering with the J.D. Salinger fan club!'."; mail($_POST['email'], 'Registration Confirmation', $body, 'From: admin@example. com'); // Clear the posted values: $_POST = []; } else { // Forgot a field. You can count how many times a substring is present in a string using the aptly named substr_count() function: if (substr_count($_POST ➝ ['email'],'@') == 1) {... With those caveats, let’s add a mail() function call to the registration page so that you get a sense of how the function might be used. To send email with PHP: 1. Open register.php (Script 8.9) in your text editor or IDE. 2. Change the email validation so that it also checks for a single “at” symbol (Script 8.10): if (empty($_POST['email']) || ➝ (substr_count($_POST['email'], ➝ '@') != 1) ) { Now the email address validation fails if the value is empty or if it doesn’t contain exactly one @. This doesn’t constitute thorough validation—far from it— but the email address becomes less of a security risk to use. See the tips for ways to improve upon this. 3. After the registration message (line 46), add the following: $body = "Thank you, {$_POST ➝ ['first_name']}, for ➝ registering with the J.D. ➝ Salinger fan club!"; mail($_POST['email'], ➝ 'Registration Confirmation', ➝ $body, 'From: admin@example. ➝ com'); continues on next page code continues on next page Creating Web Applications 229 Script 8.10 continued 57 58 59 60 61 62 63 64 65 66 67 print '

Please try again!

'; } } // End of handle form IF. // Create the form: ?> Chapter 8 B If users provide multiple email addresses A, they’ll see an error message. Sometimes the easiest way to use this function is to establish the body as a variable and then feed it into the mail() function (as opposed to writing the email’s body within the function call). The message itself is sent to the address with which the user registered, with the subject Registration Confirmation, from the address admin@example.com. If you’ll be running this script on a live server, you should use an actual email address for that site as the from value. 4. Save the file, place it in the proper directory of your PHP- and emailenabled server, and test it in your browser B. C This email was sent by the PHP script upon successful pseudo-registration. 5. Upon successfully completing the form, check your email for the message C. The “Review and Pursue” section at the end of this chapter points you in the direction of an excellent tool for validating email addresses, provided you’re using PHP version 5.2 or later. The HTML5 email input type limits the user to only entering a single email address, but that can easily be circumvented. In my PHP and MySQL for Dynamic Web Sites: Visual QuickPro Guide (Peachpit Press) and online in my forums (www.LarryUllman.com/ forums/), I discuss other ways to secure the emails that get sent by a PHP script. If you have problems receiving the PHPsent email, start by confirming that the mail server works on its own without involving PHP. Then make sure you’re using a valid from address. Finally, try using different recipient addresses, and keep an eye on your spam folder to see that the message isn’t getting put there (if applicable). continues on next page Creating Web Applications 231 It’s possible to send email with attachments or HTML email, although doing so requires far more sophisticated coding (normally involving classes and objects). Fortunately, a number of programmers have already developed workable solutions that are available for use. See Appendix B, “Resources and Next Steps,” for websites that may be of assistance. The mail() function returns a value (1 or 0) indicating its successful use. This value indicates only whether PHP was able to attempt to send the email (by using whatever email system is in place). There’s no easy way to use PHP to see whether an email address is valid or whether the end user received the message. To send an email to multiple addresses, either use the CC parameter or separate each TO address with a comma. To create new lines within the email body, either create the message over multiple lines or use the newline character (\n) within double quotation marks. If you want to send multiple headers in addition to the From address, separate them with a combination of \r\n: mail ('email@example.com', ➝ 'Testing', $body, "From: ➝ email@example.org\r\nBcc: ➝ hidden@example.net, ➝ third@example.com"); Configuring Your Server to Send Email Sending email with PHP is easy, as long as your web server (or computer) is set up to send email. If you’re using a web hosting service or your own Unix computer (such as Linux), this shouldn’t be a problem at all. If you do have a problem, contact the hosting company for support. If you’re running your own server (for example, if you’re developing locally), the ability to send email could be a sticking point. If you’re using an all-in-one installer, such as MAMP or XAMPP (see Appendix A), it should also have an email server as part of the package. If you don’t receive the email after registering, check the associated software’s documentation for what you may need to do to enable email. If you’re using a web server built into the operating system, such as Apache on Mac OS X, you may already be set up to send email. To start, go ahead and try this example using a valid email address. If you don’t receive the email, see Appendix A for information about getting mail() to work. I’ll also add that I almost never worry about getting PHP on my own computer to send out emails because I’ll never be running live websites from my computer. In other words, why waste time getting something to work that you’ll never end up using (whereas getting PHP to send out email on a live server does matter)? 232 Chapter 8 Output Buffering A handful of functions that you’ll use in this chapter and the next can be called only if nothing has been sent to the browser. These functions include header(), setcookie(), and session_start(). If you use them after the browser has already received some text, HTML, or even a blank space, you’ll get the dreaded “headers already sent” error message A. One solution that I recommend for beginning PHP developers is to make use of output buffering (also named output control). In a normal PHP script, any HTML outside the PHP tags is immediately sent to the browser. This is also true when any print statement is executed. With output buffering, the HTML and printed data—the output—will instead be placed into a buffer (that is, memory). At the end of the script, the buffer will then be sent to the browser, or if more appropriate, the buffer can be cleared without being sent to the browser. There are many reasons to use output buffering, but for beginners, one benefit is that you can use certain functions without worrying about headers already sent errors. Although you haven’t dealt with any of the named functions yet, this chapter introduces output buffering now. Using this feature will greatly reduce errors when you begin using headers (in the next section of this chapter), cookies (in the next chapter), and sessions (also in the next chapter). To begin output buffering, invoke the ob_start() function at the very top of your page. Once you call it, every print and similar function will send data to a memory buffer rather than to the browser. Conversely, HTTP calls, such as header() and setcookie(), won’t be buffered and will operate as usual. To be more explicit, it must be invoked before any print statements or any HTML gets sent to the browser. A If the browser receives any HTML prior to a header() call, you’ll see this error message. Creating Web Applications 233 At the conclusion of the script, call the ob_end_flush() function to send the accumulated buffer to the browser. Or use the ob_end_clean() function to delete the buffered data without passing it along. Both functions also turn off output buffering for that script. PHP automatically runs ob_end_flush() at the conclusion of a script if it isn’t otherwise done. But it’s still a good idea to call it yourself. From a programmer’s perspective, output buffering allows you to structure a script in a more linear form, without concern for HTTP headers. Let’s remake header.html and footer.html so that every page uses output buffering. You won’t appreciate the benefits yet, but the number of errors you won’t see over the rest of this book will go a long way toward preserving your programming sanity. To use output buffering: Script 8.11 Add output buffering to the web application by calling the ob_start() function at the top of the header.html script. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 1. Open header.html (Script 8.7) in your text editor or IDE. 18 19 20 2. At the very top of the page, before any HTML code, add the following (Script 8.11): 21 22 23 24 25 26 27 <?php // Print the page title. if (defined('TITLE')) { // Is the title defined? print TITLE; } else { // The title is not defined. print 'Raise High the Roof Beam! A J.D. Salinger Fan Club'; } ?>

Raise High the Roof Beam!

Script 8.12 Output buffering is completed at the end of the footer file using ob_end_flush(), which sends the accumulated buffer to the browser. 1 2 3 4 5 19 20 4. At the end of the script, after all the HTML, add the following (Script 8.12): This code turns off output buffering and sends the accumulated buffer to the browser. In other words, all the HTML is sent at this point. continues on next page

6 9 10 11 12 13 14 15 16 The key to using output buffering is to call the ob_start() function as early as possible in a script. In this example, you create a special section of PHP prior to any HTML and call ob_start() there. By turning on output buffering in your header file and turning it off in your footer file, you buffer every page in the application. Now print the date and time: // print date('g:i a l F j'); ?>

Creating Web Applications 235 5. Save both files, and place them in the templates directory of your PHPenabled server. 6. Test any page in your browser B. As a reminder, PHP code can be placed in a file with an .html extension—as in these two examples here—if that file is being included by a PHP script (such as index.php). For some time now, output buffering has been automatically enabled in PHP’s default configuration. The code added in this section of the chapter will work regardless of that setting. You can set the maximum buffer size in php.ini (PHP’s configuration file). The default is 4,096 bytes. The ob_get_length() function returns the length (in number of characters) of the current buffer contents. The ob_get_contents() function returns the current buffer so that it can be assigned to a variable, should the need arise. For example, you could take the accumulated content and process it to add dynamic highlighting or text manipulation. The ob_flush() function sends the current contents of the buffer to the browser and then discards them, allowing a new buffer to be started. This function lets your scripts maintain more moderate buffer sizes. The ob_clean() function deletes the current contents of the buffer without stopping the buffer process. PHP automatically runs ob_end_flush() at the conclusion of a script if it isn’t otherwise done. But it’s still a good idea to call it yourself. 236 Chapter 8 B The site works the same as it did previously, but it will be easier to work with when you use HTTP headers in the next section of this chapter. Manipulating HTTP Headers Most interactions between a server and a browser (the client) take place over HTTP (Hypertext Transfer Protocol). This is why the addresses for pages begin with http://. But HTTP communications between browsers and servers go beyond just sending HTML, images, and the like. These additional communications can be accomplished using HTTP headers. There are dozens of uses for HTTP headers, all of which you can do using PHP’s header() function. Perhaps the most common use of the header() function is to redirect the user from one page to another. To redirect the user’s browser with PHP, you send a location header: header('Location: page.php'); When using the header() function to redirect the browser, follow that line by calling exit() to cancel the execution of the script (because the browser has been redirected to another page): If you don’t invoke exit(), the rest of the script’s code will be executed, despite the fact that the browser has moved on. The most important thing to understand about using header() is that the function must be called before anything else is sent to the browser—otherwise, you’ll see the all-too-common headers already sent error message (see A in the section “Output Buffering”). If your page receives any HTML or even blank space, the header() function won’t work. Fortunately, you learned about output buffering in the previous section. Because output buffering is turned on in the application, nothing is sent to the browser until the very last line of the footer script (when ob_end_flush() is called). By using this method, you can avoid the dreaded headers already sent error message. To practice redirection, you’ll update the login page to take the user to a welcome page upon successful login. header('Location: page.php'); exit(); Creating Web Applications 237 To use the header() function: 1. Open login.php in your text editor or IDE (Script 8.8). 2. Delete the You are logged in… print statement (Script 8.13). Because the user is redirected to another page, there’s no need to include this message. 3. Where the print statement was, add the following: ob_end_clean(); header('Location: welcome.php'); exit(); The first line destroys the page buffer (because the accumulated buffer won’t be used). This isn’t strictly required but is a good idea. The next line redirects the user to welcome.php. The third line terminates the execution of the rest of the script. Script 8.13 The new version of the login page redirects the user to another page using the header() function. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 4. Save the file, and place it in the proper directory for your PHP-enabled server (along with the other scripts from this chapter). 17 18 Now you need to create the welcome.php page to which the user will be redirected. 19 20 Login Form

Users who are logged in can take advantage of certain features like this, that, and the other thing.

'; // Check if the form has been submitted: if ($_SERVER['REQUEST_METHOD'] == 'POST') { Handle the form: // if ( (!empty($_POST['email'])) && (!empty($_POST['password'])) ) { ( (strtolower($_POST['email']) if == 'me@example.com') && ($_ POST['password'] == 'testpass') ) { // Correct! 21 Redirect the user to the // welcome page! ob_end_clean(); // Destroy 22 header('Location: welcome. 23 24 25 26 27 exit(); the buffer! php'); } else { // Incorrect! print '

The submitted email address and password do not match those on file!
Go back and try again.

'; 28 29 30 } code continues on next page 238 Chapter 8 To write welcome.php: Script 8.13 continued 31 32 33 34 35 36 37 38 39 } else { // Forgot a field. print '

Please make sure you enter both an email address and a password!
Go back and try again.

'; } } else { // Display the form. print ''; 40 41 42 43 44 45 46 47 48 } include('templates/footer.html'); // Need the footer. ?> 1. Begin a new PHP document in your text editor or IDE, to be named welcome.php (Script 8.14):

Welcome to the J.D. Salinger ➝ Fan Club!

You've successfully logged ➝ in and can now take advantage ➝ of everything the site has to ➝ offer.

4. Return to PHP, and include the footer: continues on next page Script 8.14 The welcome page greets users after they’ve logged in. 1 2 3 4 5 6 7 8 9 10 11 code continues on next page Creating Web Applications 239 5. Save the script as welcome.php, place it in the same directory as the new version of login.php, and test it in your browser A, B, and C. The headers_sent() function returns TRUE if the page has already received HTTP headers and the header() function can’t be used. Script 8.14 continued 12 13 14 Using the GET method trick, you can pass values from one page to another using header(): $var = urlencode('Pass this text'); header("Location: page.php? ➝ message=$var"); The header() function should technically use a full path to the target page when redirecting. For example, it should be 15 16

Welcome to the J.D. Salinger Fan Club!

You've successfully logged in and can now take advantage of everything the site has to offer.

header('Location: http:// ➝ www.example.com/welcome.php'); or header('Location: http://localhost/ ➝ welcome.php'); In my book PHP and MySQL for Dynamic Web Sites: Visual QuickPro Guide, I show some code for dynamically generating an absolute URL based on the location of the current script. A The login form… B …and the redirection if the user properly logged in. 240 Chapter 8 C If users don’t properly log in, they remain on the login page. Review and Pursue If you have any problems with the review questions or the pursue prompts, turn to the book’s supporting forum (www.LarryUllman.com/forums/). Review n n n n n n What is the difference between include() and require()? Why can you put PHP code into an included file even when it uses an .html extension? What are the differences between relative and absolute references to a file? How do you define a constant? Are constant names case-sensitive or case-insensitive? How do you check if a constant has been defined? What is the epoch? What is a timestamp? What is the significance of $_SERVER['REQUEST_METHOD']? n n n How do you have a form element “remember” previously submitted values? How can you see a PHP error that occurs within a form element (for example, when presetting a form’s element’s value)? What does the headers already sent error mean? How can it be prevented? Creating Web Applications 241 Pursue n n n n n n Create a new prototype design for this chapter’s examples, and then create new header and footer files. View any of the site’s pages again (you should not need to change any of the PHP scripts). Change the parameters to the date() function in footer.html to display the date and/or time in a different manner. Rewrite the password conditionals found in register.php as a nested pair of conditionals. Hint: See Chapter 6 for examples. If you’re using PHP 5.2 or later, check out the PHP manual pages for the Filter extension. Then incorporate the filter_var() function to validate the email address in register.php. Change the subject and body of the email sent upon (pseudo-) registration to something more interesting and informative. Update login.php so that it also shows the form upon a failed login attempt. 242 Chapter 8 9 Cookies and Sessions Chapter 8, “Creating Web Applications,” covered a number of techniques for developing more fully realized websites. One missing piece—the focus of this chapter —is how to maintain “state” as the user traverses a multipage site. The Hypertext Transfer Protocol (HTTP) is a stateless technology, meaning that it has no built-in method for tracking a user or remembering data from one page of an application to the next. This is a serious problem, because e-commerce applications, user registration and login systems, and other common online services rely on being able to follow the same user from page to page. Fortunately, maintaining state is quite simple with PHP. This chapter discusses the two primary methods for tracking data: cookies and sessions. You’ll start by learning how to create, read, modify, and delete cookies. Then you’ll see how easy it is to master sessions, a more potent option for maintaining state. In This Chapter What Are Cookies? 244 Creating Cookies 246 Reading from Cookies 251 Adding Parameters to a Cookie 254 Deleting a Cookie 257 What Are Sessions? 260 Creating a Session 261 Accessing Session Variables 264 Deleting a Session 266 Review and Pursue 268 What Are Cookies? Prior to the existence of cookies, traversing a website was a trip without a history. Although the browser tracks the pages you visit, allowing you to use the Back button to return to previously visited pages and indicating visited links in a different color, the server does not follow what individual users see and do. This is still true for sites that don’t use cookies, as well as for users who have disabled cookies in their web browsers A. A Most browsers let users set the cookie- handling preferences. In Internet Explorer 11, you will find this in the Advanced Privacy Settings area. Debugging Cookies When you begin working with cookies in PHP, you’ll need to know how to debug your cookierelated scripts when difficulties arise. Three areas might cause you problems: .. Sending the cookie with PHP .. Receiving the cookie in your browser .. Accessing a cookie in a PHP script The first and last issues can be debugged by printing out the variable values in your PHP scripts, as you’ll soon learn. The second issue requires that you know how to work with cookies in your browser. For debugging purposes, you’ll want your browser to notify you when a cookie is being sent. This is an easy option in Internet Explorer and not readily available in the other browsers. With Internet Explorer on Windows, you can do this by choosing Internet Options under the Tools menu. Then click the Privacy tab, followed by the Advanced button under Settings. Click “Override automatic cookie handling,” and then choose Prompt for both First-party and Third-party Cookies (you can actually block the third-party cookies, if you’d rather). Other versions of Internet Explorer may use different variations on this process. Internet Explorer also has a Developer Tools window (linked under the Tools menu) that can be useful. The current versions of Chrome, Opera, Firefox, and Safari no longer offer the ability to be prompted when cookies are created, which is unfortunate. But you can view existing cookies in any browser, normally by finding the cookies area (often under Privacy) within the browser’s preferences or options. A browser’s developer tools, or third-party extensions such as Firebug, will normally show existing cookies for the site being viewed without you having to navigate through the browser settings. If you’re not using Internet Explorer, you’ll want to find what developer tools or extensions are available for your browser of choice. 244 Chapter 9 Why is that a problem? If the server can’t track a user, there can be no shopping carts for making purchases online. If cookies didn’t exist (or if they’re disabled in the browser), people wouldn’t be able to use popular sites that require user registration. In short, without cookies, there would be no Amazon or Facebook or any of the other most popular or useful sites (not in their current incarnations, at least). PHP has solid support for cookies. In this chapter, you’ll learn how to set a cookie, retrieve information from a cookie, and then delete the cookie. You’ll also see some of the optional parameters you can use to apply limits to a cookie’s existence. Before moving on, you ought to know two more things about cookies. The first is how to debug cookie-related problems. You’ll inevitably need to know how to do that, so the topic is discussed in the sidebar “Debugging Cookies.” The second is how a cookie is transmitted and received B. Cookies are stored in the browser, but only the site that originally sent a cookie can read it. Also, the cookies are read by the site when the page on that site is requested by the browser. In other words, when the user enters a URL in the address bar and clicks Go (or whatever), the site reads any cookies it has access to and then serves up the requested page. This order is important because it dictates when and how cookies can be accessed. Cookies are simply a way for a server to store information on the user’s computer. By doing so, the server can remember the user over the course of a visit or through several visits. Think of a cookie as a name tag: You tell the server your name, and it gives you a name tag. Then it can know who you are by referring back to the name tag. This brings up another point about the security issues involved with cookies. Cookies have gotten a bad rap because users believe cookies allow a server to know too much about them. However, a cookie can only be used to store information that you give it, so it’s as secure as you want it to be (although to be fair, your “giving” of information is normally not a conscious choice). The ability to send, read, and delete cookies is one of the few overlaps between server-side PHP and browser-side JavaScript. Web Browser (client) Server 1. URL Requ est ies and HTML 2. Cook 3. URL Request HTML page if(conn SELEC WHERE print PHP script and Cookies if(conn SELEC WHERE print PHP script B How cookies are sent back and forth between the server and the client. Cookies and Sessions 245 Creating Cookies An important thing to understand about cookies is that they must be sent from the server to the client prior to any other information. This means a script should send cookies before any print statement, before including an external file that contains HTML, and so forth. Should the server attempt to send a cookie after the web browser has already received HTML—even an extraneous white space—an error message will result and the cookie won’t be sent A. This is by far the most common cookie-related error. Cookies are sent using the setcookie() function: setcookie(name, value); setcookie('CookieName', 'This is the ➝ cookie value.'); That line of code sends to the browser a cookie with the name CookieName and the value This is the cookie value. B. You can continue to send more cookies to the browser with subsequent uses of the setcookie() function, although you’re limited by the browser as to how many cookies can be sent from the same site: setcookie('name2', 'some value'); setcookie('name3', 'another value'); There’s no universal, hard limit as to how many cookies a browser will accept from one site, but you should keep the number to a minimum. Finally, when creating cookies, you can—as you’ll see in this example—use a variable for the name or value attribute of your cookies: setcookie($cookie_name, ➝ $cookie_value); A A message like this is what you’ll see if the setcookie() function is called after anything, even a blank line or space, has already been sent to the browser. B If the browser is set to prompt the user for cookies, a message like this will appear for each cookie sent. (Note that the window, from Internet Explorer 11, shows the value in a URL-encoded format.) 246 Chapter 9 C This form is used to select the font size and color for use on another PHP page. For an example of setting cookies, you’ll create a script that allows the user to specify the default font size and color for a page. The page displays a form for choosing these values C and then handles the form submission D. A separate page, created in the next section of this chapter, will use these settings. To send cookies: 1. Create a new PHP document in your text editor or IDE, to be named customize.php (Script 9.1): Your settings have been entered! Now see them in action.

'; 12 code continues on next page The most critical issue with cookies is that they’re created before anything is sent to the browser. To accomplish this, the script begins with a PHP section that handles the sending of cookies. Also be certain not to have any extraneous spaces or lines before the initial PHP tag. 2. Check whether the form has been submitted: if (isset($_POST['font_size'], ➝ $_POST['font_color'])) { This page will both display and handle the form. It could use the same method explained in the previous chapter— checking if the $_SERVER['REQUEST_ METHOD'] variable has a value of POST, but as an alternative approach, the script will perform basic, minimal validation as the test for a form submission. The conditional checks for the existence of two variables: $_POST['font_ size'] and $_POST['font_color']. If both are set, the form submission will be addressed. continues on next page Cookies and Sessions 247 3. Create the cookies: setcookie('font_size', ➝ $_POST['font_size']); setcookie('font_color', ➝ $_POST['font_color']); These two lines create two separate cookies. One is named font_size and the other font_color. Their values will be based on the selected values from the HTML form, which are stored in the $_POST['font_size'] and $_POST['font_color'] variables. In a more fully developed application, you should first confirm that the variables have acceptable values. 4. Create a message and complete the conditional and the PHP section: $msg = '

Your settings have ➝ been entered! Now see them ➝ ➝ in action.

'; } // End of submitted IF. ?> When the form has been submitted, the cookies will be sent and the $msg variable will be assigned a string value. This variable will be used later in the script to print a message. This approach is necessary; you can’t print the message at this juncture because not even the HTML head has been created. 5. Create the HTML head and opening body tag: Customize Your Settings ➝ 248 Chapter 9 Script 9.1 continued 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 } // End of submitted IF. ?> Customize Your Settings

Use this form to set your preferences:

All this code must come after the setcookie() lines. Not to overstate this, but no text, HTML, or blank spaces can be sent to the browser prior to the setcookie() calls. 6. Create another PHP section to report on the cookies being sent: This code prints out a message if the cookies have been sent. The first time the user comes to the page, the cookies haven’t been sent, so $msg is not set, making this conditional FALSE, and this print invocation never runs. Once the form has been submitted, $msg has been set by this point, so this conditional is TRUE D. 7. Begin the HTML form:

Use this form to set your ➝ preferences:

The second drop-down menu is used to select the font color. The menu displays the colors in text form, but the values are HTML color values. Normally such values are written using six characters plus a pound sign (for example, #00cc00), but CSS allows you to use just a three-character version, and the pound sign will be added on the page that uses these values. continues on next page Cookies and Sessions 249 9. Complete the HTML page: 10. Save the file as customize.php, and place it in the proper directory for your PHP-enabled server. 11. Make sure you’ve set your browser to prompt for each cookie, if possible. To guarantee that the script is working, you want the browser to prompt you for each cookie, if you can. See the “Debugging Cookies” sidebar. 12. Run the script in your browser E and F. Cookies are one of the few areas in PHP that can behave differently from browser to browser or operating system to operating system. You should test your cookie-based applications on as many browsers and operating systems as you can. E The user sees this message when the first setcookie() call is made, if they’ve opted to be prompted before accepting a cookie. This cookie is storing the value of x-large in a cookie named font_size. If you use the output buffering technique taught in Chapter 8, then you can place your setcookie() calls anywhere within the script (because the browser won’t receive the data until the ob_end_flush() function is called). Cookies are limited to approximately 4 KB of total data. This is more than sufficient for most applications. To test whether it’s safe to send a cookie, use the headers_sent() function. It reports on whether HTTP headers have already been sent to the web browser. 250 Chapter 9 F The Chrome Developer Tools shows the cookies received by the browser. The second cookie that’s sent by the PHP script is named font_color and has a value of c00, representing the color gray. Script 9.2 This script sets the font size and color in CSS, using the values stored in the cookies. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 View Your Settings

Customize Your Settings

Reset Your Settings

yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda

Reading from Cookies Just as form data is stored in the $_POST array (assuming it used the POST method) and values passed to a script in the URL are stored in the $_GET array, the setcookie() function places cookie data in the $_COOKIE array. To retrieve a value from a cookie, you only need to refer to the cookie name as the index of this array. For example, to retrieve the value of the cookie established with the line setcookie('user', 'trout'); you would use the variable $_COOKIE['user']. Unless you change the cookie’s parameters (as you’ll see later in this chapter), the cookie will automatically be accessible to every other page in your web application. You should understand, however, that a cookie is never accessible to a script immediately after it’s been sent. You can’t do this: setcookie('user', 'trout'); print $_COOKIE['user']; // No value. The reason for this is the order in which cookies are read and sent (see B in the first section of this chapter). To see how simple it is to access cookie values, let’s write a script that uses the preferences set in customize.php to specify the page’s text size and color. The script relies on CSS to achieve this effect. To retrieve cookie data with PHP: 1. Begin a new PHP document in your text editor or IDE, to be named view_settings.php (Script 9.2): continues on next page Cookies and Sessions 251 View Your Settings ➝ 2. Start the CSS section: 7. Start the HTML body, and create links to two other pages:

➝ Customize Your Settings

Reset Your ➝ Settings

These two links take the user to two other PHP pages. The first, customize.php, has already been written and lets users define their settings. The second, reset.php, will be written later in the chapter and lets users delete their customized settings. 8. Add some text: A This page reflects the customized font choices made using the other PHP script.

yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda

This text exists simply to show the effects of the cookie changes. 9. Complete the HTML page: 10. Save the file as view_settings.php, place it in the same directory as customize.php, and test it in your browser A by clicking the link on customize.php. 11. View the source of the page to see the resulting CSS code B. B By viewing the source code of the page, you can also track how the CSS values change. 12. Use the customize page to change your settings and return to this script. Each submission of the form will create two new cookies storing the form values, thereby replacing the existing cookies. The value of a cookie is automatically encoded when it’s sent and decoded on being received by the PHP page. The same is true of values sent by HTML forms. Cookies and Sessions 253 Adding Parameters to a Cookie one hour (60 seconds times 60 minutes) from the current moment: Although passing just the name and value arguments to the setcookie() function will suffice for most of your cookie uses, you ought to be aware of the other arguments available. The function can take up to five more parameters, each of which limits the operation of the cookie: Because the expiration time will be calculated as the value of time() plus 3600, that argument isn’t put in quotes (you don’t want to literally pass time() + 3600 as the expiration but rather the result of that calculation). setcookie(name, value, expiration, ➝ path, domain, secure, httponly); The expiration argument is used to set a specific length of time for a cookie to exist. If it isn’t specified, the cookie will continue to be functional until the user closes the browser. Normally, you set the expiration time by adding a particular number of minutes or hours to the current time. You can find the current time in PHP by using the time() function (it returns a timestamp; see Chapter 8). Therefore, this line of code sets the expiration time of the cookie to be setcookie(name, value, time()+3600); The path and domain arguments are used to limit a cookie to a specific folder in a website—the path—or to a specific domain. Using the path option, you could limit a cookie to exist only while a user is in a specific subfolder of the domain: setcookie(name, value, time()+3600, ➝ '/subfolder/'); Cookies are already specific to a domain, so the domain argument might be used to limit a cookie to a subdomain, such as forum.example.com: setcookie(name, value, time()+3600, '', ➝ 'forum.example.com'); Script 9.3 When you add the expiration arguments to the two cookies, the cookies will persist even after users have closed out of and later returned to their browser. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Your settings have been entered! Now see them in action.

'; } // End of submitted IF. ?> code continues on next page 254 Chapter 9 Script 9.3 continued 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 Customize Your Settings

Use this form to set your preferences:

The secure value dictates that a cookie should only be sent over a secure HTTPS connection. A value of 1 indicates that a secure connection must be used, whereas 0 indicates that a secure connection isn’t necessary. You could ensure a secure cookie transmission for e-commerce sites: setcookie('cart', '82ABC3012', ➝ time()+3600, '', ➝ 'shop.example.com', 1); As with all functions that take arguments, you must pass all the values in order. In the preceding example, if there’s no need to specify (or limit) the path, you use empty quotes. With the path argument, you can also use a single slash (/) to indicate the root folder (i.e., no path restriction). By doing so, you maintain the proper number of arguments and can still indicate that an HTTPS connection is necessary. The final argument—httponly—was added in PHP 5.2. It can be used to restrict access to the cookie (for example, preventing a cookie from being read using JavaScript) but isn’t supported by all browsers. Let’s add an expiration date to the existing customize.php page so that users’ preferences will remain even after they’ve closed their browser and then returned to the site later. To set a cookie’s expiration date: 1. Open customize.php (Script 9.1) in your text editor or IDE. 2. Change the two setcookie() lines to read as follows (Script 9.3): setcookie('font_size', $_POST ➝ ['font_size'], time()+10000000, ➝ '/', '', 0); continues on next page Cookies and Sessions 255 setcookie('font_color', $_POST ➝ ['font_color'], time() ➝ +10000000, '/', '', 0); To make these cookies persist for a long time (specifically, for a couple of months), set the expiration time to be 10,000,000 seconds from now. While you’re at it, set the path argument to the root of the site (/). Doing so may improve the consistency of sending these cookies across the various browsers. Because the expiration date of the cookies is set months into the future, the user’s preferences, which are stored in the cookies, will be valid even after the user has closed and reopened the browser. Without this expiration date, users would see the default font size and color and have to reassign their preferences with every new browser session. 3. Save the file, place it in the proper directory for your PHP-enabled server, and test it again in your browser A and B. Not all browsers acknowledge a cookie’s adjusted expiration time when the cookie is being sent from your own computer (i.e., from localhost). More generally, browsers can be inconsistent in how they handle local cookies. Here are some general guidelines for what kind of expiration date to use with your cookies: If the cookie should last as long as the user browses through the site, don’t set an expiration time. If the cookie should continue to exist after the user has closed and reopened the browser, set an expiration time that’s weeks or months in the future. And if the cookie can constitute a security risk, set an expiration time of an hour or a fraction thereof so that the cookie doesn’t continue to exist too long after a user has left the browser. For security purposes, you can set a 5- or 10-minute expiration time on a cookie and have the cookie re-sent with every new page the user visits. This way, the cookie will continue to persist as long as the user is active but will automatically expire 5 or 10 minutes after the user’s last action. A The browser’s cookie reporting tools (here, Chrome’s Developer Tools) now reflect the cookie expiration dates. B The new cookie parameters don’t adversely affect the functionality of the application. 256 Chapter 9 Deleting a Cookie A How Firefox Developer Edition displays the cookie information when a deletion cookie is sent. The final thing to know about cookies is how to delete them. Although a cookie automatically expires when the user’s browser is closed or when the expiration date/time is met, sometimes you’ll want to manually delete the cookie as well. For example, websites that have registered users and login capabilities delete any created cookies when the user logs out. The setcookie() function can take up to seven arguments, but only one is required— the name. If you send a cookie that consists of a name without a value, it will have the same effect as deleting the existing cookie of the same name. For example, to create the cookie username, you use this line: setcookie('username', 'Larry'); To delete the username cookie, you code setcookie('username', ''); or setcookie('username', FALSE); As an added precaution, you can also set an expiration date that’s in the past A: setcookie('username', FALSE, ➝ time() - 6000); The only caveat when it comes to deleting a cookie is that you must use the same argument values that were used to set the cookie in the first place, aside from the value and expiration. For example, if you set a cookie while providing a domain value, you must also provide that value when deleting the cookie: setcookie('user', 'larry', ➝ time() + 3600, '', ➝ 'forums.example.com'); setcookie('user', '', time() - 600, ➝ '', 'forums.example.com'); continues on next page Cookies and Sessions 257 To demonstrate this feature, let’s add a reset page to the web application. This PHP script will destroy the sent cookies so that the user’s preferences are forgotten. 1. Begin a new PHP script in your text editor or IDE, to be named reset.php (Script 9.4): These two lines send cookies named font_size and font_color, each with no value and an expiration time of more than an hour ago. As you did when creating cookies, you must call the setcookie() function before anything else is sent to the browser. 3. Create the HTML head: Reset Your Settings ➝ 258 Chapter 9 Script 9.4 To delete the existing cookies, send new cookies with the same names, empty values, and expirations in the past. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Reset Your Settings

Your settings have been reset! Feel free to customize them again.

4. Add the page’s body:

Your settings have been reset! ➝ Feel free to customize ➝ them again.

B When the setcookie() function is used with a name but no value, the existing cookie of that name is deleted. The expiration date in the past also guarantees proper destruction of the existing cookie. The body of this script merely tells users that their settings have been reset. A link is then provided to return to the main page. 5. Complete the HTML: 6. Save the page as reset.php, place it in the proper directory for your PHPenabled server, and test it in your browser B, C, and D. C The reset page sends two blank cookies and then displays this message. To test this page, either click the appropriate link in view_settings.php (Script 9.2) or just go to this page directly. Just as creating a cookie doesn’t take effect until another page is visited, deleting a cookie doesn’t take effect until another page is visited. In other words, you can delete a cookie on a page but still access that cookie on it (because the cookie was received by the page before the delete cookie was sent). D After accessing the reset page, PHP destroys the cookies B, which will have the effect of resetting the view_settings.php page to its default formatting. Just as creating cookies has mixed results using different browsers, the same applies to deleting them. Test your scripts on many browsers and play with the setcookie() settings to ensure the best all-around compatibility. Just as one example of how different browsers handle cookies, Firefox Developer Edition treats any cookie that expires in the past as having an expiration just after the epoch B. Cookies and Sessions 259 What Are Sessions? A session, like a cookie, provides a way for you to track data for a user over a series of pages. The difference between the two—and this is significant—is that a cookie stores the data on the client (in the browser), whereas the session data is stored on the server. Because of this difference, sessions have numerous benefits over cookies: n n n n Sessions are generally more secure, because the data isn’t transmitted back and forth between the client and server repeatedly. Sessions allow you to store more information than you can in a cookie. Sessions can be made to work even if the user doesn’t accept cookies in their browser. You can more easily store other types of data in sessions, such as arrays and Booleans. When you start a session, PHP generates a random session ID. Each user’s session will have its own session ID, corresponding to the name of the text file on the server that stores the user’s session data (Script 9.5). So that every PHP script on a site can associate the same session data with a particular user, the session ID must be tracked as well. By default, this session ID is sent to the browser as a cookie A. Subsequent PHP pages will use this cookie to retrieve the session ID and access the session information. Over the next few pages, you’ll see just how easy sessions are to work with in PHP. 260 Chapter 9 A A session cookie being sent to the browser. Script 9.5 How session data is stored in a file on the server. 1 email|s:14:"me@example. com";loggedin|i:1292883103; Choosing Between Sessions and Cookies Sessions have many benefits over cookies, but there are still reasons why you would use the latter. Cookies have these advantages over sessions: .. Marginally easier to create and retrieve .. Require slightly less work from the server .. Normally persist over a longer period of time As a rule of thumb, you should use cookies in situations where security is less of an issue and only a minimum of data is being stored. If security’s a concern and there will be oodles of information to remember, you’re best off with sessions. Understand, though, that using sessions may require a little more effort in writing your scripts. Creating a Session Creating, accessing, or deleting a session begins with the session_start() function. This function will attempt to send a cookie the first time a session is started, so it absolutely must be called prior to any HTML or white space being sent to the browser. Therefore, on pages that use sessions, you should call the session_start() function as one of the very first lines in your script: Login Form

Users who are logged in can take advantage of certain features like this, that, and the other thing.

'; // Check if the form has been submitted: if ($_SERVER['REQUEST_METHOD'] == 'POST') { Handle the form: // if ( (!empty($_POST['email'])) && (!empty($_POST['password'])) ) { ( (strtolower($_POST['email']) if == 'me@example.com') && ($_ POST['password'] == 'testpass') ) { // Correct! // Do session stuff: session_start(); $_SESSION['email'] = $_POST['email']; $_SESSION['loggedin'] = time(); Redirect the user to the // welcome page! ob_end_clean(); // Destroy the buffer! header ('Location: welcome. php'); exit(); } else { // Incorrect! code continues on next page 262 Chapter 9 Script 9.6 continued 33 print '

The submitted email address and password do not match those on file!
Go back and try again.

'; 34 35 36 37 38 39 40 41 42 43 44 45 } } else { // Forgot a field. print '

Please make sure you enter both an email address and a password!
Go back and try again.

'; } } else { // Display the form. print ''; 46 47 48 49 50 51 52 53 54 } include('templates/footer.html'); // Need the footer. ?> 4. Load the form in your browser to ensure that it has no errors A. Don’t complete and submit the login form yet, because the welcome page needs to be updated prior to logging in. The php.ini configuration file includes many session-related settings that you can tinker with if you have administrative-level control over your server. Open the php.ini file in a text editor and see the manual for more information. You can also alter some of the session settings using the ini_set() function. The session_name() function lets you change the name of the session (instead of using the default PHPSESSID). It must be used before every session_start() call, like so: session_name('YourVisit'); session_start(); The session_set_cookie_params() function alters the session cookie settings, such as the expiration time, the path, and the domain. The constant SID, short for Session ID, stores a string in the format name=ID. An example is PHPSESSID= mo7puk861tm60tbm4b8coh0og2. You can store any type of value—number, string, array, or object—or any combination thereof in your sessions. A The login form. Cookies and Sessions 263 Accessing Session Variables Now that you’ve stored values in a session, you need to know how to access them. The first step is to invoke the session_start() function. This is necessary on every page that will make use of sessions, whether it’s creating a new session or accessing an existing one. From there it’s simply a matter of referencing the $_SESSION variable as you would any other array. With this in mind, you’ll write another welcome page—similar to the one from Chapter 8—that accesses the stored email and loggedin values. Script 9.7 You can access stored session values using the $_SESSION array, as long as your script uses session_start() first. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 To access session variables: 1. Create a new PHP document in your text editor or IDE, to be named welcome.php (Script 9.7): Welcome to the J.D. Salinger Fan Club!'; print '

Hello, ' . $_ SESSION['email'] . '!

'; // Print how long they've been logged in: date_default_timezone_set('America/ New_York'); print '

You have been logged in since: ' . date('g:i a', $_ SESSION['loggedin']) . '.

'; // Make a logout link: print '

Logout

'; include('templates/footer.html'); // Need the footer. ?> 4. Greet the user by email address: print '

Welcome to the J.D. ➝ Salinger Fan Club!

'; print '

Hello, ' . $_SESSION ➝ ['email'] . '!

'; To access the stored user’s address, refer to $_SESSION['email']. Here, that value is concatenated to the rest of the string that’s being printed out. 5. Show how long the user has been logged in: date_default_timezone_set ➝ ('America/New_York'); print '

You have been logged ➝ in since: ' . date('g:i a', ➝ $_SESSION['loggedin']) . ➝ '.

'; Show how long the user has been logged in, by referring to the $_SESSION['loggedin'] variable. By using this as the second argument sent to the date() function, along with the appropriate formatting parameters, you make the PHP script create text like 11:22 pm. Before using the date() function, you need to set the default time zone (this is also discussed in Chapter 8). If you want, after setting the time zone here, you can remove the use of the same function from the footer file. 6. Complete the content: print '

➝ Logout

'; The next script will provide logout functionality, so a link to it is added here. 7. Include the HTML footer, and complete the HTML page: include('templates/footer.html'); ?> 8. Save the file as welcome.php, place it in the proper directory for your PHPenabled server, and test it (starting with login.php, Script 9.6) in your browser A. To see whether a particular session variable exists, use isset($_SESSION['var']) as you would to check if any other variable is set. A more secure version of this script would both check that the variables exist (in the session) before referring to them and run the values through an escaping function before printing them. Always remember that the data stored in a session is being stored as plain text in an openly readable text file. Don’t be cavalier about what gets stored in a session, and never store sensitive information, such as credit card data, there. For added security, data can be encrypted prior to storing it in a session and decrypted upon retrieval. Doing so requires a cryptography library and more advanced PHP knowledge, however. A After successfully logging in (using me@example.com and testpass in the form), the user is redirected to this page, which greets them using the session values. Cookies and Sessions 265 Deleting a Session It’s important to know how to delete a session, just as it’s important to know how to delete a cookie: Eventually you’ll want to get rid of the data you’ve stored. Session data exists in two places—in an array during the execution of the script and in a text file—so you’ll need to delete both. But first you must begin with the session_start() function, as always: session_start(); Then, you clear the session variables by resetting the $_SESSION array: $_SESSION = []; // Or = array(); Finally, remove the session data from the server (where it’s stored in temporary files). To do this, use session_destroy(); With that in mind, let’s write logout.php, which will delete the session, effectively logging out the user. To delete a session: 1. Start a new PHP script in your text editor or IDE, to be named logout.php (Script 9.8).

Welcome to the J.D. Salinger Fan Club!

You are now logged out.

Thank you for using this site. We hope that you liked it.
Blah, blah, blah... Blah, blah, blah...

this function call to $_SESSION, all the existing key-value pairs in $_SESSION will be erased. A The logout page destroys the session data. 4. Destroy the session data on the server: session_destroy(); This step tells PHP to remove the actual session file on the server. 5. Include the HTML header, and complete this PHP section: define('TITLE', 'Logout'); include('templates/header.html'); ?> 6. Make the page content:

Welcome to the J.D. Salinger ➝ Fan Club!

You are now logged out.

Thank you for using this site. ➝ We hope that you liked it.
Blah, blah, blah... Blah, blah, blah...

7. Include the HTML footer: 8. Save the file as logout.php, place it in the proper directory for your PHPenabled server, and test it in your browser by clicking the link in welcome.php A. To delete an individual session value, use unset($_SESSION['var']); An additional step would be to delete the session cookie too. The PHP module on the server will automatically perform garbage collection based on settings in its configuration. PHP uses garbage collection to manually delete session files from the server, with the assumption that they’re no longer needed. Cookies and Sessions 267 Review and Pursue n If you have any problems with the review questions or the pursue prompts, turn to the book’s supporting forum (www.LarryUllman.com/forums/). Review n n n n n n Where does a cookie store data? Where does a session store data? Which is generally more secure? Name two debugging techniques when trying to solve issues involving cookies. How do the path and domain arguments to the setcookie() function affect the accessibility of the cookie? How do you delete a cookie? n n n What function must every page call if it needs to assign or access session data? Why do sessions also use cookies (by default)? Pursue n n n Make sure you know what developer tools exist for your browser of choice, and how to basically use them. Look up the PHP manual page for the setcookie() function. Review the information and user comments there for added instructions on cookies. 268 Chapter 9 n Rewrite customize.php so that the script also applies the user’s preferences. Hint: You need to take into account the fact that the cookies aren’t available immediately after they’ve been set. Instead, you would write the CSS code using the $_POST values after the form has been submitted, the $_COOKIE values upon first arriving at the page (if the cookies exist), and the default values otherwise. Make the form in customize.php sticky so that it reflects the user’s current choices. Rewrite welcome.php so that the print statement that greets the user by email address uses double quotation marks. For an added challenge, rewrite welcome.php so that the print statement that indicates how long the user has been logged in also uses double quotation marks. Hint: You’ll need to use a variable. Update welcome.php so that it confirms a session variable exists before it attempts to use it. Also run the session values through an escaping function— see Chapter 5, “Using Strings”—to prevent XSS attacks. Rewrite the last three scripts so that the session uses a custom name. 10 Creating Functions Throughout this book, you’ve used dozens of functions that provide much-needed functionality, such as date(), setcookie(), and number_format(). Although those functions have already been defined by PHP, here you’ll be creating your own. However, functions you’ve created and those built into PHP are used in the same manner. Defining your own functions can save you oodles of time as a programmer. In fact, they constitute a big step in the process of creating web applications and building a solid library of PHP code to use in future projects. In this chapter, you’ll see how to write your own functions that perform specific tasks. After that, you’ll learn how to pass information to a function, use default values in a function, and have a function return a value. You’ll also learn how functions and variables work together. In This Chapter Creating and Using Simple Functions 270 Creating and Calling Functions That Take Arguments 276 Setting Default Argument Values 282 Creating and Using Functions That Return a Value 285 Understanding Variable Scope 290 Review and Pursue 296 Creating and Using Simple Functions As you program, you’ll discover that you use certain sections of code frequently, either within a single script or over the course of several scripts. Placing these routines into a self-defined function can save you time and make your programming easier, especially as your websites become more complex. Once you create a function, the actions of that function take place each time the function is called, just as print sends text to the browser with each use. The syntax for creating a user-defined function is function function_name() { statement(s); } For example: function whatever() { print 'whatever'; } You can use roughly the same naming conventions for functions as you do for variables, just without the initial dollar sign. Second to that is the suggestion that you create meaningful function names, just as you ought to write representative variable names. For example, create_header would be a better function name than function1. Remember not to use spaces in the name, though—doing so constitutes two separate words for the function name, which will result in error messages. The underscore is a logical replacement for the space. Unlike variables, function names in PHP are not case-sensitive, but you should still stick with a consistent naming scheme. 270 Chapter 10 Any valid PHP code can go within the statement(s) area of the function, including calls to other functions. Functions do not have a limit on the number of statements they can contain, but make sure you end each statement with a semicolon, just as you would within the rest of the PHP script. Functions can also contain any combination of control structures: conditionals and loops. A These pull-down menus are created by a user-defined PHP function. The exact formatting of a function isn’t important as long as the requisite elements are there. These elements include the word function, the function’s name, the opening and closing parentheses, the opening and closing braces, and the statement(s). It’s conventional to indent a function’s statement(s) from the function keyword line, for clarity’s sake, as you would with a loop or conditional. In any case, select a format style that you like—which is both syntactically correct and logically sound— and stick to it. You call (or invoke) the function by referring to it just as you do any built-in function. The line of code whatever(); will cause the statement part of the previously defined function—the print command —to be executed. Let’s begin by creating a function that generates month, day, and year pull-down menus for a form A. Creating Functions 271 To create and call a basic function: 1. Start a new PHP document in your text editor or IDE, to be named menus.php (Script 10.1): Date Menus 2. Begin the PHP section: 'January', ➝ 'February', 'March', 'April', ➝ 'May', 'June', 'July', ➝ 'August', 'September', ➝ 'October', 'November', ➝ 'December']; // Make the month pull-down menu: print ''; To generate a list of months, first create an array of the month names, indexed numerically, beginning at 1 for January. When you specify the index for the first array element, the others will follow sequentially without the need to be explicit in naming them. 272 Chapter 10 After the array has been created, the initial select tag is printed out. Then, a foreach loop runs through the $months array. For each element in the array, the HTML option tag is printed, using each element’s key (the numbers 1 through 12) as the option value and each element’s value (January through December) as the displayed text. Each line is also preceded by a newline character (\n) so that each option starts on its own line within the HTML source. 5. Create the day pull-down menu: print ''; The day menu is a lot easier to create. To do so, use a simple for loop, running through the numbers 1 through 31. 6. Create the year pull-down menu: print ''; To create the year pull-down menu, start by using the date() function to get the current year. Then create options for this year plus the next 10, using a for loop. continues on page 274 Script 10.1 The function defined in this script creates three pull-down menus for a form. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 Date Menus 'January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']; // Make the month pull-down menu: print ''; // Make the day pull-down menu: print ''; // Make the year pull-down menu: print ''; } // End of make_date_menus() function. // Make the form: print ''; ?> Creating Functions 273 7. Close the function: } // End of make_date_menus() ➝ function. When you’re creating functions, it’s easy to create parse errors by forgetting the closing brace. You may want to add comments to help you remember this final step. 8. Make the form tags, and call the function: print ''; The print statements are used to create the HTML form tags. Without a form, the date pull-down menus won’t appear properly in the script. Once you’ve created your function, you simply have to call it by name—being careful to use the exact spelling—to make the function work. Be sure to include the parentheses as well. 9. Complete the PHP and HTML: ?> 10. Save the file as menus.php, place it in the proper directory for your PHPenabled server, and run it in your browser A. 11. If you want, check out the HTML source of the page to see what was dynamically generated B. B The source of the page shows the HTML created by the print statements in the make_date_menus() function. 274 Chapter 10 If you see a “Call to undefined function: some_function…” error message, it means you’re trying to call a function that doesn’t exist C. If you’re trying to call a PHP function, either you misspelled the name or it’s not supported on your version of PHP. Check the PHP manual for more. If you’re calling a user-defined function when you see this error, either it hasn’t been defined or you’ve misspelled it. Recheck your spelling in both the definition of the function and its usage to see if you made a mistake. The function_exists() function returns TRUE or FALSE based on whether a function exists in PHP. This applies to both user-defined functions and those that can be built into PHP: if (function_exists ➝ ('some_function')){ ... Although you aren’t required to, I recommend that you habitually define your functions at the beginning of a script (or in an included file), rather than at the end of the script. Some people prefer this syntax for laying out their functions: function function_name() { statement(s); } User-defined functions add extra memory requirements to your PHP scripts, so you should be judicious in using them. If you find that your function merely calls another PHP function or has but one line of code, it’s probably not the best use of this capability. C This error means that the PHP script does not have access to a function defined under the given name. In this case, the problem is due to a missing “s” in the function call: make_date_menus() versus make_date_menu(). Creating Functions 275 Creating and Calling Functions That Take Arguments Although being able to create a simple function is useful, writing one that takes input and does something with that input is even better. The input passed to a function is known as an argument. This is a concept you’ve seen before: The sort() function takes an array as an argument, which the function then sorts. The syntax for writing functions that take arguments is as follows: function function_name ➝ ($arg1,$arg2, ...) { statement(s); } The function is defined with parameters: variables that are assigned the values sent to the function when you call it. The variables are defined using the same naming rules as any other variable in PHP: function make_full_name($first, ➝ $last) { print $first . ' ' . $last; } Functions that take input are called much like those that don’t—you just need to remember to pass along the necessary values. You can do this either by passing variables: make_full_name($fn, $ln); or by sending literal values, as in make_full_name('Larry', 'Ullman'); or some combination thereof: make_full_name('Larry', $ln); 276 Chapter 10 The important thing to note is that arguments are passed quite literally: The first variable in the function definition is assigned the first value in the call line, the second function variable is assigned the second call value, and so forth A. Functions aren’t smart enough to intuitively understand how you meant the values to be associated. This is also true if you fail to pass a value, in which case the function will assume that value is null (null isn’t the mathematical 0, which is actually a value, but closer to the idea of the word nothing). The same thing applies if a function takes two arguments and you pass one—the second will be null, which might create an error B. (To clarify a minor point, the variables in the function definition are known as parameters; the values passed to the function when invoked are known as arguments. That being said, it’s common enough to use the terms interchangeably.) To demonstrate functions that take arguments, let’s create a more interesting example. In Chapter 8, “Creating Web Applications,” you learned how to make forms “sticky”: having them remember their values from previous submissions. The code for a sticky text input might be First Name: continues on next page function make_full_name($first, $last) { print $first . ' ' . $last; } make_full_name($fn, $ln); make_full_name('Larry', 'Ullman'); make_full_name('Larry', $ln); A How values in function calls are assigned to function arguments. B As with any function (user-defined or built into PHP), passing an incorrect number of arguments when calling it yields warnings. Creating Functions 277 Since many forms, such as register.php from Chapter 8, repeatedly use similar code, you have a good candidate for a user-defined function. This next script will define and call a function that creates sticky text inputs. The function will take one argument for the input’s name, and another for the input’s label (its textual prompt). The function will be called multiple times by the script to generate multiple inputs C. Upon form submission, the previously entered values will be remembered D. C These three form inputs are created by a user-defined function. To create and call a function that takes an argument: 1. Start a new PHP document in your text editor or IDE, to be named sticky1.php (Script 10.2): Sticky Text Inputs ➝ 2. Begin the PHP section: Sticky Text Inputs ' . $label . ': '; // Begin the input: print '

'; } // End of make_text_input() function. // Make the form: print ''; ?> Creating Functions 279 4. Print an opening paragraph and a label tag: print '

' . $label . ➝ ': '; The code being generated by this function will be essentially like that just indicated (and in Chapter 8), but it will be wrapped in a paragraph tag and the input’s label will be formally placed within label tags. The value of the label (for example, First Name) will be passed to the function when the function is called. 5. Begin the text input: print ' wasn’t created), so another clause—specifically value="whatever"—can still be added. But that clause should only be added if $_POST['input_name'] is set, so the conditional checks for that. As with the code in Chapter 8, the value is printed only after being run through htmlspecialchars(). 280 Chapter 10 7. Complete the input, the label, the paragraph, and the function: print '>

'; } // End of make_text_input() ➝ function. 8. Make the form tags, and call the function: print '

'; make_text_input('first_name', ➝ 'First Name'); It’s important that the form uses the POST method, because the function checks for existing values in $_POST. You can actually omit an action value, in which case the form will automatically be submitted back to the same page. To create a “first name” input, call the make_text_input() function, passing it the name the input should have and an appropriate label. 9. Create two more inputs: make_text_input('last_name', ➝ 'Last Name'); make_text_input('email', 'Email ➝ Address'); Now the script has used the same function three times, in three different ways. The result will be three distinct text inputs. Note that although HTML5 has an email input type, for the sake of simplicity, only plain text inputs are being created. 10. Complete the form: print '

'; The form needs a submit button in order to test the sticky feature. Declaring Parameter Types PHP 7 supports the ability to declare parameter types to indicate what kind of value must be passed. To use this feature, provide the type—bool, float, int, or string—before the parameter name: function make_full_name(string ➝ $first, string $last) { With that code in place, PHP will return an error if the function is called while provided with non-string arguments: make_full_name(12, true); ➝ // Error! Earlier versions of PHP supported type hinting, which was similar but did not support scalar variable types such as string and int. This type of stricter function definition is best when you want to guarantee the type of value passed to a function. 11. Complete the PHP and HTML: ?> 12. Save the file as sticky1.php, place it in the proper directory for your PHPenabled server, and run it in your browser C and D. You can define as many functions as you want, not just one per script as the examples in this chapter portray. A function is not limited as to the number of arguments it can take. Once you’ve defined your own functions like this, you can place them in an external file and then require that file when you need access to the functions. Creating Functions 281 Setting Default Argument Values PHP allows functions to have default argument values: Just assign a value to the parameter in the function definition: function greeting($who = 'world') { print "

Hello, $who!

"; } Such a function will use the preset value unless it receives a value that then overwrites the default. In other words, by setting a default value for an argument, you render that particular argument optional when calling the function. You’d set an argument’s default value if you wanted to assume a certain value but still allow for other possibilities A: greeting(); greeting('Zoe'); (Note: This isn’t really a good use of a user-defined function, or a default argument value, but it’s easily understood as an example.) The parameters with default values must always be written after the other parameters (those without default values). This is because PHP directly assigns values to parameters in the order they’re received from the call line. Thus, it isn’t possible to omit a value for the first argument but include one for the second. For example, suppose you have function calculate_total($qty, ➝ $price = 20.00, $tax = 0.06) {... If you call the function with the line calculate_total(3, 0.07); with the intention of setting $qty to 3, leaving $price at 20.00, and changing the $tax to 0.07, there will be problems. The result will be that $qty is set to 3, $price is set to 0.07, and $tax remains at 0.06 B, which isn’t the desired outcome. The proper way to achieve that effect would be to code calculate_total(3, 20.00, 0.07); Let’s rework the make_text_input() function to incorporate the notion of setting default argument values. A Calling the function without any arguments uses the default value (the first greeting); calling it with an argument provided means that value will be used instead (the second). function calculate_total($qty, $price = 20.00, $tax = 0.06) { // Make the calculations. } calculate_total(3, 0.07); B Because of the way function arguments work, you cannot “skip” an argument when calling a function. 282 Chapter 10 Script 10.3 The function now takes three arguments, but only two of them are required. If no $size is passed to the function, its value will be 20. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 Sticky Text Inputs ' . $label . ': '; // Begin the input: print '

'; } // End of make_text_input() function. // Make the form: print '

'; code continues on next page Creating Functions 283 4. Change the function calls to vary the sizes: make_text_input('first_name', ➝ 'First Name'); make_text_input('last_name', ➝ 'Last Name', 30); make_text_input('email', 'Email ➝ Address', 50); Now the first input will use the default size, and the others will be longer. 5. Save the script as sticky2.php, place it in the proper directory of your PHPenabled server, and test it in your browser C. Script 10.3 continued 35 36 37 38 39 40 41 42 43 44 // Create some text inputs: make_text_input('first_name', 'First Name'); make_text_input('last_name', 'Last Name', 30); make_text_input('email', 'Email Address', 50); print ''; ?> To pass no value to a function for a particular argument, use an empty string ('') or the word NULL (without quotes). Either of these values will override the default value, if one is established. As mentioned way back in Chapter 1, “Getting Started with PHP,” the PHP manual marks optional function arguments using square brackets. For example, when you use the number_format() function, the number of decimals to round to is optional: string number_format(float number ➝ [, int decimals = 0]) 284 Chapter 10 C Now the function is capable of changing the size of the input, based on an argument. If no value is provided for that argument, the default size is used instead (the first input). Creating and Using Functions That Return a Value A This simple form takes two values on which calculations will be made. Functions do more than take arguments; they can also return values. Doing so requires just two more steps. First, you use the return statement within the function. Second, you use the output somehow when you call the function. Commonly, you’ll assign the returned value to a variable, but you can also, for example, directly print the output. Here is the basic format for a function that takes two arguments and returns a value: function make_full_name ➝ ($first, $last) { $name = $first . ' ' . $last; return $name; } B The result of the calculation, which takes place within a user-defined function. This function could be used like so: $full_name = make_full_name ➝ ($fn, $ln); There the returned value of the function is assigned to a variable. Here it’s printed immediately: print make_full_name($fn, $ln) To best demonstrate this concept, let’s create a function that performs a simple calculation and formats the result. This script will display an HTML form where a user enters a quantity and price A. When the form is submitted (back to this same page), a total value will be calculated and printed B. Creating Functions 285 To create and use a function that returns a value: 1. Create a new PHP document in your text editor or IDE, to be named calculator1.php (Script 10.4): Cost Calculator 2. Begin the PHP code: Your total comes to ➝ $$total.

"; This part of the PHP code—which handles the form if it has been submitted—first checks that a numeric quantity and price were entered. If so, the total is determined by calling the calculate_total() function and assigning the result to the $total variable. This result is then printed out. continues on page 288 Script 10.4 This script both displays and handles an HTML form in order to perform some basic calculations. The script uses a function that takes two arguments and returns a single value. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 Cost Calculator Your total comes to $$total.

"; } else { // Inappropriate values entered. print '

Please enter a valid quantity and price!

'; } } ?>

Quantity:

Price:

Creating Functions 287 6. Complete the conditionals: } else { print '

Please enter a valid ➝ quantity and price!

'; } } If either of the form variables was not properly submitted, a message is printed indicating that. The final brace closes the form submission conditional. A little CSS is applied to both printed messages (here and in Step 5). 7. Display the HTML form: ?> The form itself is quite simple, requesting two different values from the user A. Because this form is created outside of the main submission conditional, the form will always be displayed by the page B. 8. Complete the HTML page: 288 Chapter 10 Returning Multiple Values User-defined functions frequently return just a single value but can return multiple values by using arrays. Here’s how you go about this: function some_function($p1, $p2) { // Do whatever. return [$a, $b]; // Or: return array($v1, $v2); } Then, to call this function, use the list() function to assign the array elements to individual variables: list($v1, $v2) = some_function ➝ ($a1, $a2); The result is that $a from the function is assigned to $v1 in the PHP script, and $b from the function is assigned to $v2. Declaring Return Types PHP 7 supports the ability to declare the type of value returned by a function. To use this feature, follow the function name with a colon and the type returned: function make_full_name ➝ ($first, $last): string { Or function calculate_total ➝ ($quantity, $price): float { This type of stricter function definition is best when you want to guarantee the type of value returned by a function. 9. Save the page as calculator1.php, place it in the proper directory for your PHP-enabled server, and test it in your browser B. You can have only one return statement executed in a function, but the same function can have multiple return statements. As an example, you may want to write a function that checks for a condition and returns a value indicating whether the condition was satisfied. In such a case, the function might contain if (condition) { return true; } else { return false; } The result returned by the function is either TRUE or FALSE, indicating whether the stated condition was met. Creating Functions 289 Understanding Variable Scope The concept of variable scope wasn’t introduced in earlier chapters because without an understanding of functions, scope makes little sense. Now that you are acquainted with functions, this section revisits the topic of variables and discusses in some detail just how variables and functions work together. As you saw in the second section of this chapter, “Creating and Calling Functions That Take Arguments,” you can send variables to a function by passing them as arguments. However, you can also reference an external variable from within a function using the global statement. This is possible because of variable scope. The scope of a variable is the realm in which it exists. By default, the variables you write in a script exist for the life of that lone script. Conversely, environment variables, such as $_SERVER['PHP_SELF'], exist throughout every PHP script on the server. Functions, though, create a new level of scope. Function variables—the function’s parameters as well as any variables defined within the function—exist only within that function and aren’t accessible outside of it. Put another way, function variables are local variables with local scope. Likewise, a variable from outside a function is not available within the function, by default A. Even when a variable is used as an argument to a function call, that variable’s value is being passed to the function, not the variable itself. You can, however, make a variable external to a function available within the function by using the global statement. The global statement roughly means, “I want this variable within the function to refer to the same named variable outside of the function.” In other words, the global statement turns a local variable with local scope into a global variable with global scope. Any changes made to the variable within the function are also reflected by the variable outside of the function, without using the return command (assuming the function is called, of course). A Adding function definitions to a script adds another area of variable scope. 290 Chapter 10 The syntax of the global statement is simply function function_name($args) { global $variable; statement(s); } There is another issue regarding functions and variables: Because of variable scope, a local variable within a function is a different entity—perhaps with a different value—than a variable outside of the function, even if the two variables use the exact same name. Let’s look at this more explicitly… Say you have: function foo($param) { // Do whatever. } $var = 1; foo($var); When the function is called, the value of $var will be assigned $param, so their values are the same but their names are different and they are different variables. Now if the name of the parameter in the function is also $var— function bar($var) { // Do whatever. } $var = 1; bar($var); then the $var variable within the function is assigned the same value as the original $var outside of the function—but they’re still two separate variables. The one has a scope within the function, and the other has a scope outside of it. This means that you can use the same name for variables in the function as exist outside of the function without conflict. Creating Functions 291 Just remember they aren’t the same variable. What happens to a variable’s value within a function only affects that variable within the function. Here’s an example B: function add_one($n) { $n++; print 'Added one!
'; } $n = 1; print "\$n equals $n
"; add_one($n); print "\$n equals $n
"; This is all true unless you use the global statement, which does make the two variables the same C: function add_one() { global $n; // Same! $n++; print 'Added one!
'; } $n = 1; print "\$n equals $n
"; add_one(); print "\$n equals $n
"; Note that in this case, the variable’s value no longer needs to be passed to the function either. To demonstrate variable scope, let’s rework the calculator1.php script using the global statement. 292 Chapter 10 B Changes to a local variable inside a function have no effect on a similarly named global variable. C Changes made to a global variable inside of a function will change the variable outside of that function. Script 10.5 The function in this script can use the $tax variable—even though it hasn’t been passed to the function—thanks to the global statement. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Cost Calculator Your total comes to ➝ $$total, ➝ including the $tax percent tax ➝ rate.

"; The $tax variable defined at the beginning of the script is printed out at the end. If you hadn’t used the $taxrate variable within the function and made the alterations to the global $tax instead, those calculations would be reflected in the value printed here. 6. Save the script, place it in the proper directory for your PHP-enabled server, and test it in your browser D and E. Script 10.5 continued 35 36 37 38 39 40 41 42 43 44 45 46 Constants and the superglobal arrays ($_GET, $_POST, $_COOKIE, and $_SESSION) have the added benefit that they’re always available inside functions without requiring the global statement. This is why they are known as superglobals. 48 Each function has its own, separate local scope. 50 51 52 294 Chapter 10 47 49 // Call the function and print the results: $total = calculate_ total($_POST['quantity'], $_POST['price']); rint "

Your total comes p to $$total, including the $tax percent tax rate.

"; } else { // Inappropriate values entered. print '

Please enter a valid quantity and price!

'; } } ?> Add A Quotation 2. Create a section of PHP code, and identify the file to be used: Add A Quotation Your quotation has been stored.

'; } else { // Could not open the file. print '

Your quotation could not be stored due to a system error.

'; } code continues on next page Script 11.1 continued 30 } else { // Failed to enter a quotation. print '

Please enter a quotation!

'; 31 32 33 34 35 36 37 38 39 40 41 42 43 44 } This simple conditional validates the user-supplied data. The first part confirms that the $_POST['quote'] variable isn’t empty. The second part confirms that the variable doesn’t still have the default value (as shown in A). 5. Confirm that the file can be written to: } // End of submitted IF. if (is_writable($file)) { // Leave PHP and display the form: ?> By placing this function call in a conditional, you make the PHP script attempt to write to the file only if the file is writable. 6. Write the data to the file, and then print a message: file_put_contents($file, ➝ $_POST['quote'] . PHP_EOL, ➝ FILE_APPEND); print '

Your quotation has been ➝ stored.

'; The first line writes the user-submitted data to the file. The PHP_EOL constant is concatenated to the written data, so that each submission gets stored on its own line. 7. Complete the conditionals: } else { // Could not open ➝ the file. print '

Your quotation ➝ could not be stored ➝ due to a system error. ➝

'; } } else { // Failed to enter ➝ a quotation. print '

Please enter a ➝ quotation!

'; } } // End of submitted IF. continues on next page Files and Directories 307 The first else completes the conditional that checks if PHP could open the file for writing B. If you see this message, there’s likely a permissions issue or the file reference is incorrect. The second else completes the conditional that checks whether no quotation was entered C. The final closing brace marks the end of the main submission conditional. If you’d rather, you can replace the inline CSS with an actual CSS class declaration. B If the PHP script can’t find the quotes.txt file, or if it’s not writable, the user will see this message. Because this page handles the form and then displays it again (so that the user may keep entering quotations), the form isn’t displayed as part of an else statement as it has been in other examples in this book. 8. Complete the PHP section: ?> Because the rest of this script is standard HTML, exit out of the PHP code by closing the PHP tag. 9. Create the HTML form: This HTML form presents a text box where the user can enter a quotation. The text box has a preset value of Enter your quotation here., created by putting that text between the textarea tags. 308 Chapter 11 C The script includes basic form validation. 10. Complete the HTML page: 11. Save the file as add_quote.php, and place it in the proper directory for your PHP-enabled server. Again, refer back to B in the previous section, “File Permissions,” of this chapter for how add_quote.php and quotes.txt should be placed on your server relative to each other. If this arrangement isn’t possible for you, or if it’s just too confusing, then place both documents within the same directory (the one from which you can execute PHP scripts), and change the $file assignment line to $file = 'quotes.txt'; 12. Run the script several times in your browser D and E. 13. If you want, open the quotes.txt file in a text editor to confirm that the data has been written to it. Note that all of the file- and directoryrelated functions are usable only on files and directories on the same computer (i.e., server) on which PHP is running. A PHP script on a server has no access to a file on a client’s computer (until the file is uploaded to the server). If you receive a permissions error when you run this script B, either the permissions aren’t set properly or the PHP script couldn’t access the data file. The latter can happen if you misspell the filename or incorrectly reference the file’s path on the server. If your version of PHP is running in safe mode or has the open_basedir directive set, you may be limited in using PHP to access files and directories. Check your phpinfo() script to see these settings for your server. D Filling out the form… E …and the result if all went well. Files and Directories 309 Locking Files Although the last example worked fine (hopefully), it could be improved on. If only a single user were submitting the form at one time, there would be no problems. But what if two or more users submitted different quotations simultaneously? In such a case, there could be problems when multiple instances of the PHP script attempt to write to the same text file at once. The file could become corrupted. When there’s a risk of multiple scripts writing to the same file at once, the solution is to temporarily lock the file while PHP is writing to it. To do that, add the LOCK_EX constant as the third argument to file_put_contents(): file_put_contents($file, $data, ➝ LOCK_EX); To use both the LOCK_EX and FILE_APPEND constants, separate them with the bitwise OR operator (|): file_put_contents($file, $data, ➝ FILE_APPEND | LOCK_EX); It doesn’t matter in which order you provide the two constants (see the sidebar “Bitwise Operators”). The different lock types are represented by the constants listed in Table 11.2. A shared lock, LOCK_SH, is for reading from a file, which means it’s okay if multiple files use the file at the same time (all with shared locks). Conversely, the exclusive lock, LOCK_EX, means only the locking file should have access. The LOCK_UN constant is for releasing any type of lock. It’s provided to the flock() function, not used in this chapter (see the PHP manual for more information). 310 Chapter 11 TABLE 11.2 flock( ) Lock Types Lock Meaning LOCK_SH Shared lock for reading purposes LOCK_EX Exclusive lock for writing purposes LOCK_UN Release of a lock LOCK_NB Nonblocking lock Bitwise Operators A lesser-known but often useful set of operators are the bitwise operators. Beginners will most likely use them in situations where constants are passed as arguments, as in the file locking example. Bitwise operators work with bits—the smallest data type, also referred to as binary digits. The operators look and function like the standard ones: bitwise & instead of &&, bitwise | instead of ||. Bitwise operators are often used with constants like LOCK_EX and FILE_APPEND because each constant represents a numeric value. The numeric value in turn is a type of flag indicating what’s allowed. The code FILE_APPEND | LOCK_EX therefore says to apply whatever flags are represented by the FILE_APPEND or the LOCK_EX constants. Note that you should unlock the file once the script is done with it, although PHP will kindly unlock it for you should you forget. To demonstrate, let’s update add_quote.php to lock the file during the writing process. Script 11.2 The modified version of the add_quote.php script locks the data file for better security and reliability. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 Add A Quotation Your quotation has been stored.

'; } else { // Could not open the file. print '

Your quotation could not be stored due to a system error.

'; } code continues on next page Files and Directories 311 3. Save the file, place it in the proper directory for your PHP-enabled server, and test it again in your browser A and B. Technically, if a file is opened in an appending mode, as in this example, not locking it probably won’t be a problem even if multiple scripts are writing to the file simultaneously. That said, better safe than sorry! For file locking to be reliable, every script that writes to a file needs to use locking. Script 11.2 continued 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 } else { // Failed to enter a quotation. print '

Please enter a quotation!'; } } // End of submitted IF. // Leave PHP and display the form: ?>

A Using the form once again… B …the quotation is still stored without a problem. 312 Chapter 11 Reading from Files Now that you’ve created a script that writes data to a file, it’s time to create one that can read the information. There are a number of ways to read from a file; which approach you take depends on what your needs are. To read an entire file in as one string, use file_get_contents(): $data = file_get_contents($file); Alternatively, if the file has some data on each line, as is the case with quotes.txt, you’re better off using the file() function: $data = file($file); The file() function is a valuable built-in tool in PHP. It reads everything from a file and, unlike file_get_contents(), returns that information as an array. Each array element contains one line from the file, where each line is terminated by a newline (\n or \r\n). If the document represented by $file contains two lines of information, each of which ends with a newline, the corresponding array will contain two elements. The first element will be equal to the first line of $file, and the second element will be equal to the second line. Once the data is stored into an array, you can easily manipulate or print it, as you learned in Chapter 7, “Using Arrays.” Next, let’s use this knowledge to create a script that randomly displays one of the stored quotations. Files and Directories 313 To read from a file: 1. Create a new PHP document in your text editor or IDE, to be named view_quote.php (Script 11.3): View A Quotation

Random Quotation

2. Open a PHP code section: View A Quotation

Random Quotation

' . trim($data[$rand]) . '

'; ?> If $data has 10 elements, they’re indexed between 0 and 9, so that’s the range to use for rand(). Therefore, to calculate the range for a variable number of lines in the text file, use 0 and 1 less than the number of elements in $data. A A random quotation is displayed each time the page is viewed. B Subsequent viewings of the view_quote.php script display different quotations from the text file. 5. Print out the quotation: print '

' . trim($data ➝ [$rand]) . '

'; A simple print statement involving concatenation is used to print the random quotation. To retrieve the quotation, you refer to the $data array and use the generated $rand number as the index. The retrieved quotation is then trimmed to cut off the newline characters from the end of the quotation. 6. Complete the PHP code and the HTML page: ?> 7. Save the file as view_quote.php, place it on your web server (in the same directory as add_quote.php), and test it in your browser A. 8. Reload the page in your browser to view another random quote B. If you want to be extra careful, you can use the is_readable() function to test that PHP can read a file before you call the file() function (although it’s rare that a file isn’t readable). The readfile() function reads through a file and immediately sends the contents to the output buffer. This means that with output buffering enabled, the file’s contents get added to the buffer. With output buffering disabled, the file’s contents go straight to the browser. Later in this chapter, you’ll learn a more complex method of reading a file using fgets() and fgetcsv(). Files and Directories 315 Handling File Uploads As this book has demonstrated, handling HTML forms using PHP is a remarkably easy achievement. Regardless of the data being submitted, PHP can handle it easily and directly. The same is true when the user uploads a file via an HTML form. To give the user the option of uploading a file, you must make three changes to the standard HTML form. First, the initial form tag must include the code enctype="multipart/form-data", which lets the browser know to expect different types of form data:

The form must also always use the POST method. Second, a special hidden input type should be added to the form: This tells the browser how large a file, in bytes, can be uploaded. Third, the file input is used to create the necessary form field A and B: The file type of form input allows users to select a file on their computer, which, upon submission, will be uploaded to the server. Note that the file input should be placed after the MAX_FILE_SIZE hidden input. 316 Chapter 11 A This is how Chrome interprets the file input type (prior to selecting a file). B This is how Internet Explorer interprets the file input type. TABLE 11.3 FILE Error Codes Code Meaning 0 No error has occurred. 1 The file exceeds the upload_max_filesize setting in php.ini. 2 The file exceeds the MAX_FILE_SIZE setting in the HTML form. 3 The file was only partially uploaded. 4 No file was uploaded. 6 No temporary directory exists. 7 Failed write to disk. 8 Upload prevented by an extension. Once you’ve configured the HTML form and the user has submitted a file through it, you can then use PHP to handle the file. In the PHP script, you refer to the $_FILES variable (think of it as the file equivalent of $_POST) to reference the uploaded file. The $_FILES array contains five elements: n name, the name of the file as it was on the user’s computer n type, the MIME type of the file (for example, image/jpg) n n n size, the size of the file in bytes tmp_name, the temporary name of the file as it’s stored on the server error, an error code if something goes wrong (Table 11.3; note that, as strange as this may seem, there is no error code 5). When a file is uploaded, the server first places it in a temporary directory. You should then use the move_uploaded_file() function to move the file to its final destination: move_uploaded_file($_FILES ➝ ['picture']['tmp_name'], ➝ '/path/to/dest/filename'); The first argument is the temporary name of the file on the server, found in $_FILES['input_name']['tmp_name']. The second argument is the full path and name of the destination. continues on next page Files and Directories 317 For PHP to be able to take these steps, you must set several configurations in the php.ini file (see the “Configuring PHP for File Uploads” sidebar), and the web server needs write access to both the temporary and the final destination directories. (PHP should have write access to the temporary directory by default.) Next, you’ll write a basic script that uploads a file and stores it on the server. Like the add_quote.php script, this example also both creates the HTML form C and processes it, all in one page. First, though, you’ll create a writable directory as the destination point. C This HTML form lets users select a file on their computer to upload to the server. To create a writable directory: 1. Create a new folder named uploads, located outside the web directory root D. 2. Using the steps outlined in the first section of this chapter, “File Permissions,” set the permissions so that everyone can write to, read from, and search (0777 in Unix terms) the directory. D For this example, a writable uploads directory must exist. Here, it’s placed in the same directory as the web root folder. Thus, uploads is in the directory above the one in which the upload_file.php script resides and is not accessible via HTTP. Configuring PHP for File Uploads In order for file uploading to work, a number of settings in your php.ini configuration file must be set. These may or may not be enabled in your configuration, so you should check them by viewing the php.ini file or running a phpinfo() script. For starters, file_uploads must be on. Second, the upload_tmp_dir value must be set to a directory on the server where PHP can place files (in other words, it must exist and be modifiable by the web server). If this setting has no value, that’s probably fine (meaning that a hidden directory created expressly for purposes such as these will be used). The upload_max_filesize and post_max_size settings dictate how large a file can be sent, such as 512 KB or 2 MB. Whereas the MAX_FILE_SIZE hidden form input is a recommendation to the browser, these two settings control whether the file is uploaded. Finally, if really large files—many megabytes or larger—will be uploaded, you may need to increase the memory_limit and max_execution_time settings to give PHP the time and the resources to do what it needs to do. 318 Chapter 11 Again, if you’re running Windows you likely don’t need to do anything (try the next script to see for sure). If you’re running another operating system, check the list of bullet points in the first section of the chapter for the suggestion that works for your situation. To use PHP for file uploads: 1. Create a new PHP document in your text editor or IDE, to be named upload_file.php (Script 11.4): 2. Create a section of PHP code: Upload a File continues on page 321 Script 11.4 This script handles a file upload by first defining the proper HTML form and, second, invoking move_uploaded_file() to move the file to the desired location. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Upload a File Your file has been uploaded.

'; } else { // Problem! print '

Your file could not be uploaded because: '; // Print a message based upon the error: switch ($_FILES['the_file']['error']) { case 1: print 'The file exceeds the upload_max_filesize setting in php.ini'; break; case 2: print 'The file exceeds the MAX_FILE_SIZE setting in the HTML form'; break; case 3: print 'The file was only partially uploaded'; break; case 4: print 'No file was uploaded'; break; case 6: print 'The temporary folder does not exist.'; break; default: print 'Something unforeseen happened.'; break; } print '.

'; // Complete the paragraph. } // End of move_uploaded_file() IF. } // End of submission IF. // Leave PHP and display the form: ?>

Upload a file using this form:

input type="hidden" name="MAX_FILE_SIZE" value="300000"> <

Chapter 11 4. Attempt to move the uploaded file to its final destination: if (move_uploaded_file ➝ ($_FILES['the_file'] ➝ ['tmp_name'], "../uploads/ ➝ {$_FILES['the_file'] ➝ ['name']}")) { The move_uploaded_file() function attempts to move the uploaded file (identified by $_FILES['the_file'] ['tmp_name']) to its new location (../ E If the file was uploaded and moved successfully, a message is printed and the form is displayed again. uploads/{$_FILES['the_file'] ['name']). The location is the uploads directory, which is in the folder above the one this script is in. The file’s name will be the same as it was on the user’s computer. Placing this function as a condition in an if statement makes it easy to respond based on whether the move worked. Note that there is an implicit trust here that the user is uploading a file that’s safe for you to put onto your server retaining the same name. See the tips for suggestions on how to make this process more secure. 5. Print messages indicating the success of the operation: print '

Your file has been ➝ uploaded.

'; } else { // Problem! print '

➝ Your file could not be ➝ uploaded because: '; The first print statement is executed if the move worked E. The else applies if it didn’t work, in which case an error message is begun. This message will be made more explicit in Step 6. continues on next page Files and Directories 321 6. Print out the error message if the move didn’t work: switch ($_FILES['the_file'] ['error']) { case 1: print 'The file exceeds the ➝ upload_max_filesize setting ➝ in php.ini'; break; case 2: print 'The file exceeds the ➝ MAX_FILE_SIZE setting in ➝ the HTML form'; break; case 3: print 'The file was only ➝ partially uploaded'; break; case 4: print 'No file was uploaded'; break; case 6: print 'The temporary folder ➝ does not exist.'; break; default: print 'Something unforeseen ➝ happened.'; break; } If a move doesn’t work, the $_FILES['the_file']['error'] variable contains a number indicating the appropriate error message. When you use this in a switch conditional, the PHP script can print out the appropriate error message F. You wouldn’t normally place code like this in a public site—it’s a little too much information—but it’s exceptionally good for helping you debug a problem. 322 Chapter 11 F If a problem occurred, the script indicates the cause. 7. Complete the error message, and close both conditionals: print '.

'; // Complete paragraph. } // End of move_uploaded_ ➝ file() IF. } // End of submission IF. ➝ the 8. Exit out of PHP, and create the HTML form: ?> The HTML form is simple, containing only two visible elements: a file input type and a submit button. It differs from other HTML forms in this book in that it uses the enctype attribute and a MAX_FILE_SIZE hidden input type. Be careful when giving your file input a name, because this value must exactly match the index used in the $_FILES variable. Here, you use a generic the_file. 9. Complete the HTML page: continues on next page Files and Directories 323 10. Save the page as upload_file.php, place it in the proper directory for your PHP-enabled server relative to the uploads directory D, and test it in your browser G. Only files smaller than about 300 KB should be allowed, thanks to the MAX_FILE_SIZE restriction. 11. Inspect the uploads directory to ensure that the file was placed there. If the file couldn’t be moved and a permissions denied error is shown, check the permissions on the uploads directory. Then check that the path to the directory used in the script is correct and that there are no spelling errors. As you might discover, files uploaded through the browser are owned—in terms of permissions—by the web server application, which put them there. From a security standpoint, it’s better to rename an uploaded file. To do so, you’ll need to devise a system that generates a new, unique filename and stores both the original and new filenames in a text file or a database. A script can handle multiple file uploads as long as they have different names. In such a case, you need only one MAX_FILE_SIZE hidden input. In the PHP script, you’d apply the move_uploaded_file() function to $_FILES['filename1'], $_FILES['filename2'], and so on. You can limit a file upload to a specific size or type by referencing the appropriate index (for example, $_FILES['the_file'] ['size']) in your PHP script (after the file has been uploaded). Use unlink() to delete a file without moving or copying it. You can use the copy() function to make a copy of a file on the server. 324 Chapter 11 G Select a file on your computer to upload. Navigating Directories The previous PHP scripts work with files, but you can also do many things with directories using PHP. In this example, you’ll write a script that lists a directory’s contents, but first you’ll need to understand the usage and syntax of many of the functions you’ll use. To find all the contents of a directory, the easiest option is to use the scandir() function: $stuff = scandir($dir); This function returns an array of every item—directory or file—found within the given directory. As with the file-related functions, the value of $dir can be a relative or an absolute path to the directory in question. A The list_dir.php script shows the contents of a directory. The top part lists the subfolders, and the bottom table lists the files. This next example uses scandir(), but let’s look at a couple more functions first. You’ll use the filesize() function in this example; it determines how large a file is in bytes. This value can be assigned to a variable or be printed: $size = filesize($file); Similarly, the filemtime() function retrieves the modification time of a file. It returns a timestamp, which can be formatted using the date() function. Finally, PHP includes several functions that identify attributes. This chapter has already mentioned is_writable() and is_readable(), but there are also is_dir() and is_file(). They return TRUE if the item in question is a directory or a file, respectively. You’ll put all of these capabilities together into one page, which will constitute a web-based control panel for viewing a directory’s contents A. Files and Directories 325 To create the directory control panel: 1. Create a new PHP document in your text editor or IDE, to be named list_dir.php (Script 11.5): Directory Contents</ title> </head> <body> Script 11.5 This script displays the contents of a directory. First the subdirectories are listed, followed by the files (with their sizes and modification dates) in a table. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 <!doctype html> <html lang="en"> <head> <meta charset="utf-8"> <title>Directory Contents Directories

$item

'; // Close the list. code continues on next page 326 Chapter 11 Script 11.5 continued 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 // Create a table header: print '

Files

'; // List the files: foreach ($contents as $item) { if ( (is_file($search_dir . '/' . $item)) AND (substr($item, 0, 1) != '.') ) { // Get the file size: fs = filesize($search_dir . $ '/' . $item); // Get the file's modification date: lm = date('F j, Y', $ filemtime($search_dir . '/' . $item)); // Print the information: print " \n"; } // Close the IF. } // Close the FOREACH. 2. Begin the PHP code, and set the time zone: '; // Close the HTML table. ?> Files and Directories 327 4. List the subdirectories of this directory: print '

Directories

$item

'; This foreach loop accesses every item in the array, assigning each one to the $item variable. The script should first list every directory, so the is_dir() function is called to confirm the item’s type. That same conditional also checks that the current item isn’t the current directory or a hidden directory—both marked by a single period on Unix systems—or the parent directory, marked by a double period on Unix systems. If this conditional is TRUE, then the item’s name is printed out, within list item tags, followed by a newline (to make for neater HTML source code). So that the is_dir() function will work when dealing with items found in other directories, the $search_dir value, plus a slash, is appended to each item. If the code just referred to $item without adding the directory path, the code would only work for the current directory. 5. Create a new heading, and start a table for the files: print '

Files

Name	Size	Last Modified
$item	$fs bytes	$lm

'; 328 Chapter 11 The script also displays the files’ sizes and modification dates. To make this look nicer, the results are placed in an HTML table. 6. Begin looping through the files in this directory: foreach ($contents as $item) { if ( (is_file($search_dir . '/' ➝ . $item)) AND (substr($item, ➝ 0, 1) != '.') ) { Another foreach loop is used to go through the directory contents again. This time, the conditional only wants items that are files, but not hidden files that begin with a single period. Again, the $search_dir value and a slash is prepended to each item. 7. Calculate the file’s size and modification date, and then print out the information: $fs = filesize($search_dir . '/' ➝ . $item); $lm = date('F j, Y', filemtime ➝ ($search_dir . '/' . $item)); print "\n"; The first line calls the filesize() function to retrieve the file’s size in bytes. The second line calls the filemtime() function, which returns a timestamp of the file’s modification time. The timestamp is then fed into the date() function, along with the proper formatting, to return a string like November 24, 2016. Finally, these two items and the file’s name are printed in the appropriate columns of the table. For additional security, you can also apply htmlspecialchars() to the item’s name when printing it. 8. Complete the conditional and the loop: } } 9. Close the table: print '

Name	Size	Last Modified
$item	$fs bytes	$lm

'; 10. Complete the PHP code and the HTML page: ?> 11. Save the file as list_dir.php, place it in the proper directory for your PHPenabled server, and test it in your browser A. 12. If you want, change the value of $search_dir, and retest the script in your browser B. B The directory listing for another folder on the server. Notice that you need to use double backslashes to create absolute path names on a Windows server. This is necessary because the single backslash, used in Windows path names, is the escape character. So, it must be escaped to be taken literally: C:\\myfiles\\directory The glob() function lets you search a directory for files whose name matches a pattern (like something.jpg or filename.doc). Other file functions you might appreciate include fileperms(), which returns the file’s permissions; fileatime(), which returns the last time a file was accessed; and fileowner(), which returns the user who owns the file. The basename() and dirname() functions are useful for finding subparts of a full directory or file path. The finfo_file() function is the best way to find a file’s MIME type. Files and Directories 329 Creating Directories Understanding how to read from and write to files on the server is only part of the data storage process. It’s likely you’ll want to read from and write to directories as well. The command for creating a directory in PHP is mkdir(): mkdir('directory_name', ➝ permissions); The directory name is the name of the directory to be created. This value can be relative to the current directory (i.e., the one the script is in), or it can be a full path: mkdir('C:\\inetpub\\users\\rey'); On Windows servers, the permissions are ignored and therefore not required (as in the preceding example). On non-Windows servers, the permissions are 0777 by default (see the section “File Permissions” earlier in this chapter to learn what those numbers mean). With this in mind, let’s create a script that makes a new directory for a user when the user registers—the theory being that a user could upload files to that directory. This script also records the username and password to a text file so that the user can be validated when logging in. You’ll begin by creating the parent directory, which must be writable so that PHP can create subdirectories in it, and the users.txt data file. 330 Chapter 11 To create the directory and the data file: 1. Create a new folder named users, located outside of the web directory root. It could be created in the same directory as the uploads folder made earlier (see D in “Handling File Uploads”). 2. Using the steps outlined in the first section of this chapter, “File Permissions,” set the permissions so that everyone can write to, read from, and search (0777 in Unix terms) the directory. If you’re running Windows, this step will most likely not be necessary. 3. In your text editor, create a new, blank document. 4. Save this file in the users directory with the name users.txt. 5. Again using the steps outlined earlier in the chapter, set the permissions on users.txt so that everyone can write to and read from the file (0666 in Unix terms). Again, this will probably not be necessary if you’re running Windows on your PHP server. Once you create a directory that PHP can write to, PHP should be able to automatically create a users.txt file in that directory to which PHP can write. However, it’s best not to make assumptions about such things. To create the registration script: 1. Begin a new PHP document in your text editor or IDE, to be named register.php (Script 11.6): Register

Register

In the page’s head, a CSS class is defined that will be used to format errors. continues on page 333 Script 11.6 The register.php script serves two purposes: It records the user’s information in a text file and creates a new directory for that user’s stuff. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Register

Register

Please enter a username!

'; } if (empty($_POST['password1'])) { $problem = TRUE; print '

Please enter a password!

'; } if ($_POST['password1'] != $_POST['password2']) { $problem = TRUE; print '

Your password did not match your confirmed password!

'; } if (!$problem) { // If there weren't any problems... if (is_writable($file)) { // Open the file. // Create the data to be written: subdir = time() . rand(0, 4596); $ $data = $_POST['username'] . "\t" . sha1(trim($_POST['password1'])) . "\t" . $subdir . PHP_EOL; // Write the data: file_put_contents($file, $data, FILE_APPEND | LOCK_EX); // Create the directory: mkdir ($dir . $subdir); // Print a message: print '

You are now registered!

'; } else { // Couldn't write to the file. print '

You could not be registered due to a system error.

'; } } else { // Forgot a field. print '

Please go back and try again!

'; } } else { // Display the form. // Leave PHP and display the form: ?> code continues on next page 332 Chapter 11 Script 11.6 continued 68 69 70 71 72 73 74 75 76 77 2. Begin the PHP code, and create two variables: Please ➝ enter a username!

'; } if (empty($_POST['password1'])) { $problem = TRUE; print '

Please ➝ enter a password!

'; } if ($_POST['password1'] != $_POST ['password2']) { $problem = TRUE; print '

Your ➝ password did not match your ➝ confirmed password!

'; } continues on next page Files and Directories 333 The registration form is a simpler version of earlier registration forms developed in this book. The same validation process you previously developed is used to check the submitted username and passwords. The $problem variable is used as a flag to indicate whether a problem occurred. 5. Check for problems: if (!$problem) { Again, the $problem variable lets you know if it’s okay to register the user. If no problems occurred, it’s safe to continue. 6. Confirm that the users.txt file is writable: if (is_writable($file)) { Like before, the data file is first confirmed as writable in a conditional so that the script can respond accordingly. 7. Create the data to be written to the file, and then write it: $subdir = time() . rand(0, 4596); $data = $_POST['username'] . ➝ "\t" . sha1(trim($_POST ➝ ['password1'])) . "\t" . ➝ $subdir . PHP_EOL; file_put_contents($file, $data, ➝ FILE_APPEND | LOCK_EX); The name of the directory being created is a number based on the time the user registered and a random value. This system helps guarantee that the directory created is unique and has a valid name. 334 Chapter 11 A The result if the users.txt file is not writable. Instead of storing a single string, as you previously have, this script stores three separate pieces of information: the user’s name; an encrypted version of the password (using the sha1() function; see the “Encrypting Passwords” sidebar); and the directory name, created in the preceding line. The password is trimmed first, to get rid of any extraneous spaces. To distinguish between the pieces of information, you insert a tab (created using the \t code). A newline is used to mark the end of the line, again using the PHP_EOL constant. 8. Create the user’s directory, and print a message: mkdir($dir . $subdir); print '

You are now ➝ registered!

'; B The script reports any form validation errors. The mkdir() function creates the directory in the users directory. The directory is named whatever random number was generated earlier. 9. Complete the conditionals: } else { // Couldn't write to the file. print '

You ➝ could not be registered due ➝ to a system error.

'; } } else { // Forgot a field. print '

Please ➝ go back and try again!

'; } The first else completes the conditional if the script couldn’t open the users.txt file for writing A. The second else completes the conditional if the user failed to complete the form properly B. Files and Directories 335 10. Add an else clause to the main conditional, and exit out of PHP: } else { ?> Unlike the previous examples in this chapter, this PHP script first displays the form and then handles it. Whereas the other scripts would then display the form again, this one does not, because the form creation is part of an else statement. The rest of the page is just HTML, so you exit out of PHP to create the form. 11. Display the HTML form: 12. Complete the main conditional: This final closing curly bracket closes the main submit conditional. For it to work, a new PHP section must first be created. 13. Complete the HTML page: 336 Chapter 11 C The registration form is quite basic but serves its purpose. D This is what the user sees if the registration process worked. 14. Save the file as register.php, place it in the proper directory for your PHPenabled server, and test it in your browser C and D. 15. If you want, open the users.txt file in your text editor to see its contents (Script 11.7). You can also ensure that the page worked as it should by looking in the users directory for the new subdirectories. The rmdir() function deletes an existing directory, assuming PHP has permission to do so. When using a character, such as the tab, to separate stored values, you should additionally take measures to escape or strip that character from the stored values. Script 11.7 The users.txt file lists three tab-delineated fields of information: the username, a scrambled version of the user’s password, and the user’s associated directory name. 1 2 3 4 5 larry 9d4e1e23bd5b727046a9e3b4b7db57bd8d6ee684 14615086124319 john 5baa61e4c9b93f3f0682250b6cf8331b7ee68fd8 14615086364092 paul f0578f1e7174b1a41c4ea8c6e17f7a8a3b88c92a 14615086461481 george 81fe8bfe87576c3ecb22426f8e57847382917acf 14615252264106 ringo c2543fff3bfa6f144c2f06a7de6cd10c0b650cae 1461525233328 Encrypting Passwords The sha1() function creates a hash: a mathematically calculated representation of a string. So the registration script doesn’t actually store the password but stores a representation of that password (in theory, no two strings would have the same sha1() value). You’ll soon see how the hashed password is used by a login script. That being said, the sha1() does not create a secure representation of the password. For modern computers, it’s far too easy to perform the calculations necessary to crack passwords hashed with sha1(). But the book does use sha1() as an easy approach, with the expectation that you wouldn’t replicate this in a real-life application. The current, most secure solution for password management is to use PHP’s built-in password_ hash() and password_verify() functions. Although not overly complex, they are a bit involved for beginners, especially if you’re not using at least PHP 5.5 or greater. When you’re ready to implement your own login capability, see the PHP manual pages for these functions to learn how to use them. Files and Directories 337 Reading Files Incrementally In the view_quote.php script (Script 11.3), an entire file was read into an array using the file() function. But what if you want to read in only a little of the file at a time? Then you need to use the fgets() function. The fgets() function reads a string of a certain length. It’s most often placed in a while loop that uses the feof() function to make sure the end of the file hasn’t been reached. For example: $fp = fopen($file, 'rb'); while (!feof($fp)) { $string = fgets($fp, 1024); } fclose ($fp); With that code, 1,023 bytes of data at a time will be read in, as fgets() always reads 1 byte less than the length you specify. Or fgets() will stop reading once it reaches the end of the line or the end of the file. The second argument is optional, but if present, it should be a number larger than a single line of text in the file. If you want to just read to the end of the line, omit the length argument: $string = fgets($fp); In an example where the data is stored in a delineated format (commonly using a comma, hence a CSV—comma-separated values—format), you can use the fgetcsv() function instead. It breaks the string into parts, using the marked separator, and returns an array: $array = fgetcsv($fp, length, ➝ delimiter); $array = fgetcsv($fp, 1024); 338 Chapter 11 Again, the preceding function call returns 1023 bytes of data, but it breaks the string into an array using the default delimiter—a comma—as an indicator of where to make elements. This function is the equivalent of using the fgets() and explode() functions together. If you provide a delimiter argument, you can change what character is used to delineate the data. Finally, because these functions rely on identifying the end of a line, it’s a smart extra precaution to enable PHP’s auto_detect_line_endings setting. You can do so using the ini_set() function: ini_set('auto_detect_line_endings', ➝ 1); As an example, let’s create a login script that uses the users.txt file created in the preceding example. It will continue to read a file until a matching username/password combination has been found. To read a file incrementally: 1. Begin a new PHP document in your text editor or IDE, to be named login.php (Script 11.8): Login

Login

2. Create the PHP section, and identify the file to use: Login

Login

You are now logged in.

'; } else { print '

The username and password you entered do not match those on file.

'; } } else { // Display the form. // Leave PHP and display the form: ?> 7. Check the submitted values against the retrieved values: if ( ($line[0] == $_POST ➝ ['username']) AND ($line[1] == ➝ sha1(trim($_POST ➝ ['password']))) ) { This two-part conditional checks the submitted username against the stored username ($line[0]) and checks the submitted password against the stored password ($line[1]). However, because the stored password was scrambled using sha1(), apply sha1() to the submitted value and then make the comparison. 8. If a match was found, set $loggedin to TRUE, and exit the while loop: $loggedin = TRUE; break; If the conditional is TRUE, the submitted username and password match those on file. In this case, the $loggedin flag is set to TRUE, and the break statement is used to exit the while loop. The benefit of this system is that only as much of the file is read as is required to find a match. 9. Close the conditional, the while loop, and the file: } } fclose ($fp); 10. Print a message to the user: if ($loggedin) { print '

You are now logged ➝ in.

'; } else { print '

➝ The username and password you ➝ entered do not match those on ➝ file.

'; } Using the $loggedin flag, the script can now say whether the user is “logged in.” You could add some functionality to this process by storing the user’s directory in a session and then sending them to a file-upload page. 11. Continue the main submit conditional, and exit PHP: } else { ?> 12. Create the HTML form: continues on next page Files and Directories 341 13. Return to PHP to complete the main conditional: 14. Finish the HTML page: 15. Save the file as login.php, place it in the proper directory for your PHPenabled server, and test it in your browser A, B, and C. A The login form takes a username and password. As of PHP 5.3, the fgetcsv() function takes another optional argument: the character used to escape problematic characters. Naturally, the default escape character is the backslash. If a line is blank, fgetcsv() returns an array containing a single null value. B If the submitted username and password match those previously recorded, the user sees this message. C The result if the user submits a username and password combination that doesn’t match the values previously recorded. 342 Chapter 11 Review and Pursue If you have any problems with the review questions or the pursue prompts, turn to the book’s supporting forum (www.LarryUllman.com/forums/). Review n n n n n n n n n n What version of PHP are you running? What steps did you need to take to make a file or directory writable for your server? What is the web root directory (as a concept)? What is the web root directory for your website (whether on your own computer or on a live server)? What are two ways you can write data to a file? How do you append new data to existing files (as opposed to replacing any existing data)? How do you ensure that new data is placed on its own line? In order for a form to accept file uploads, what attributes must the opening form tag have? In what variable will a PHP script be able to access an uploaded file? What function is used to move the file to its final destination on the server? How does the fgetcsv() function differ from file() or file_get_contents()? Is sha1() a secure method for hashing data? Files and Directories 343 Pursue n n n n n n n Check out some of the other filesystemrelated functions in the PHP manual (start at www.php.net/manual/en/ ref.filesystem.php). n n Modify add_quote.php so that it confirms that the quotes.txt file exists prior to checking if it’s writable. Make the text area in add_quote.php sticky. Change add_quote.php so that it takes the quotation and the attribution as separate inputs and writes them separately to the text file. Then modify view_quote.php so that it retrieves and displays both pieces of data. Modify view_quote.php so that it displays two random quotations. Update upload_file.php, making it confirm that the uploads directory is writable. View the PHP manual page for the glob() function to see what it can do and how to use it. 344 Chapter 11 n n Update list_dir.php to display other information about the files in a directory. Create a system to guarantee unique usernames in register.php. Hint: Before you attempt to create the directory, use PHP to check your list of existing usernames for a match to the just-registered name. If no match is found, the new name is acceptable. If the username is already in use, then PHP can create an error message requesting a new username. Use the combination of writing to and reading from text files, plus either sessions or cookies, to create a real registration and login system. When you’re ready for a bigger challenge, rewrite register.php and login.php to use the password_hash() and password_verify() functions. 12 Intro to Databases The Internet wouldn’t be what it is today if not for the existence of databases. In fact, PHP probably wouldn’t be as popular or as useful if not for its built-in support for numerous types of databases. This chapter will use MySQL as the example database management system (DBMS). Although MySQL—which is available for most platforms—may not be as powerful as the highest-end commercial database servers, it has enough speed and functionality for most purposes. And its price—free for most uses—makes it the common choice for web development. This chapter walks through the development of a simple database for running a basic blog. Although you’ll learn enough here to get started working with databases, you’ll want to visit Appendix B, “Resources and Next Steps,” once you’ve finished this chapter to find some references where you can learn more about the topic. In This Chapter Introduction to SQL 346 Connecting to MySQL 348 MySQL Error Handling 352 Creating a Table 355 Inserting Data into a Database 360 Securing Query Data 366 Retrieving Data from a Database 371 Deleting Data in a Database 376 Updating Data in a Database 382 Review and Pursue 388 Introduction to SQL TABLE 12.1 Common SQL Commands A database is a collection of tables (made up of columns and rows) that stores information. Most databases are created, updated, and read using SQL (Structured Query Language). SQL has surprisingly few commands (Table 12.1 lists the seven most important), which is both a blessing and a curse. Command Purpose ALTER Modifies an existing table CREATE Creates a database or table DELETE Deletes records from a table DROP Deletes a database or table INSERT Adds records to a table SELECT Retrieves records from a table SQL was designed to be written a lot like the English language, which makes it very user friendly. But SQL is still extremely capable, even if it takes some thought to create more elaborate SQL statements with only the handful of available terms. In this chapter, you’ll learn how to execute all the fundamental SQL commands. UPDATE Updates records in a table For people new to PHP, confusion can stem from PHP’s relationship to HTML (i.e., PHP can be used to generate HTML, but PHP code is never executed in the browser). When you incorporate a database, the relationships can become even fuzzier. The process is quite simple: PHP is used to send SQL statements to the database application, where they are executed. The result of the execution—the creation of a table, the insertion of a record, the retrieval of some records, or even an error—is then returned by the database to the PHP script A. With that in mind, PHP’s mysqli_query() function will be the most-used tool in this chapter. It sends an SQL command to MySQL: $result = mysqli_query(database ➝ connection, SQL command); 346 Chapter 12 Database application if(conn SELEC WHERE print 1. SQL query 2. Result of execution PHP script A PHP will be used to send an SQL statement to MySQL. MySQL will execute the statement and return the result to the PHP script. MySQL Support in PHP Support for the MySQL database server has to be built into PHP in order for you to use PHP’s MySQL-specific functions. For most PHP installations, this should already be the case. You can confirm support for MySQL by calling the phpinfo() function, which reveals details of your installation. When working through this chapter, if you see an error message saying … undefined function mysqli_…, this means the version of PHP you’re using doesn’t have support for MySQL (or you misspelled the function name, which you should also check). Enabling support for MySQL takes a little effort, but it can be done if you have administrative-level control over your server. For more information, see the PHP manual. I start this chapter with this prologue because the addition of SQL and MySQL to the web development process will complicate things. When problems occur—and undoubtedly they will—you’ll need to know how to solve them. When a PHP script that interacts with a MySQL database does not perform as expected, the first step is to determine if the problem is in the query itself—number 1 in A—or in the results of the query— number 2 in A. To take this step, you can start by printing out the query being executed, using code such as the following: print $query; Assuming that $query represents the complete SQL command, often containing the values of PHP variables, this one simple line will reveal to you the actual SQL statement being run. Next, you would take the printed query and execute it using another application. The two most common options are n n The MySQL client B, a command-line tool for interacting with MySQL phpMyAdmin C, a PHP-based MySQL interface One or both of these should be provided to you by your hosting company or the software you installed on your own computer. For a demonstration of using each, see Appendix A, “Installation and Configuration.” Technically, a DBMS, or database application, is the software that interfaces with the database proper. However, a lot of people use the terms database and DBMS synonymously. Lots of other applications are available for interacting with MySQL aside from the MySQL client and phpMyAdmin. Some are free, and others cost. A quick search using Google for MySQL, admin, and your operating system should turn up some interesting results. B The MySQL client comes with the MySQL database software and can be used to execute queries without the need for a PHP script. C phpMyAdmin is perhaps the most popular software written in PHP. It provides a web-based interface for a MySQL database. Intro to Databases 347 Connecting to MySQL When you worked with text files in Chapter 11, “Files and Directories,” you saw that some functions, such as fwrite() and fgets(), require that you first create a file pointer using fopen(). This pointer then acts as a reference to that open file. You use a similar process when working with databases. First, you have to establish a connection to the database server—in this case, MySQL. This connection is then used as the access point for any future commands. The syntax for connecting to a database is $dbc = mysqli_connect(hostname, ➝ username, password, ➝ database_name); The database connection—assigned to $dbc in this example—is normally established using at least four arguments: the host, which is almost always localhost; the username; the password for that username; and the database name. If you’re using a database through a hosting company, the company will most likely provide you with all of these values. If you’re running MySQL on your own computer, see Appendix A to learn how you create a user and a database before proceeding. Once you’re finished working with a database, you can close the connection, just as you’d close an open file: mysqli_close($dbc); The PHP script will automatically close the database connection when the script terminates, but it’s considered good form to formally close the connection once it’s no longer needed. 348 Chapter 12 For the first example of this chapter, you’ll write a simple script that attempts to connect to the MySQL database. Once you have this connection working, you can proceed through the rest of the chapter. Again, you’ll need to already know the right hostname, username, password, and database values in order to execute this example. And the database will need to have been created! To connect to a MySQL database: 1. Begin a new PHP document in your text editor or IDE, to be named mysqli_connect.php (Script 12.1): Connect to MySQL 2. Start the section of PHP code: Successfully ➝ connected to the database! ➝

'; mysqli_close($dbc); } else { print '

➝ Could not connect to the ➝ database.

'; } Script 12.1 Being able to connect to the MySQL database is the most important step. This script tests that process. 1 2 3 4 5 6 7 8 9 10 11 12 Connect to MySQL Successfully connected to the database!

'; 15 16 17 18 19 20 21 22 23 24 25 26 ysqli_close($dbc); // Close the m connection. } else { print '

Could not connect to the database.

'; } ?> By placing the connection attempt as the condition in an if-else statement, you make it easy to report on whether the connection worked. This chapter will continue to use username and password as values. For your scripts, you’ll need to replace these with the values provided by your web host or set them when you add a user using the steps outlined in Appendix A. The database being used in this chapter is named myblog. It will need to be created prior to executing this script, either by your hosting company or by yourself (see Appendix A). If a connection was established, a positive message is printed and then the connection is closed. Otherwise, a message stating the opposite is printed, and there is no need to close the database connection (because it wasn’t opened). 4. Complete the PHP code and the HTML page: ?> continues on next page Intro to Databases 349 5. Save the file as mysqli_connect.php, place it in the proper directory of your PHP-enabled computer, and test it in your browser A. If you see results like those in B, double-check the username and password values. They should match up with those provided to you by your web host or those you used to create the user. You can always test your connection username and password by using them in the MySQL client (again, see Appendix A). A If PHP has support for MySQL and the username/password/host/database combination you used was correct, you should see this simple message. If you see call to undefined function mysqli_connect…, your version of PHP doesn’t support MySQL (see the “MySQL Support in PHP” sidebar). B If PHP couldn’t connect to MySQL, you’ll probably see something like this. The warning message may or may not appear, depending on your error management settings. 350 Chapter 12 The localhost value is used as the hostname when both the PHP script and the MySQL database reside on the same computer. You can use PHP to connect to a MySQL database running on a remote server by changing the hostname in the PHP script and creating the proper permissions in MySQL. PHP has built-in support for most databases, including MySQL, SQLite, MongoDB, Oracle, and PostgreSQL. If you’re using a type of database that doesn’t have direct support—for example, Access or SQL Server—you’ll need to use PHP’s ODBC (Open Database Connectivity) functions along with that database’s ODBC drivers to interface with the database. The combination of using PHP and MySQL is so common that you may run across terms that identify servers configured with both PHP and MySQL: LAMP, MAMP, and WAMP. These stand for the operating system—Linux, Mac OS X, or Windows—plus the Apache web server, the MySQL DBMS, and PHP. You’ll be working with MySQL, so all the functions you use in this chapter are MySQL specific. For example, to connect to a database in MySQL the proper function is mysqli_connect(), but if you’re using PostgreSQL, you’d instead write pg_connect(). If you aren’t using a MySQL DBMS, use the PHP manual (available through www.PHP.net) to find the appropriate function names. You don’t have to select the database when connecting, but it’s more common to do so. The most likely exception is if your application uses multiple databases. You haven’t done so in these examples, but in general it’s a good idea to set your database information—hostname, username, password, and database name—as variables or constants. Then you can plug them into the appropriate functions. By doing so, you can separate the database specifics from the functionality of the script, allowing you to easily port that code to other applications. Intro to Databases 351 MySQL Error Handling Before this chapter gets too deep into working with MySQL, it would be best to discuss some error-handling techniques up front. Common errors you’ll encounter are n Failure to connect to MySQL n Inability to run a query n No results returned by a query n Data not inserted into a table Experience will teach you why these errors normally occur, but immediately seeing what the problem is when running your scripts can save you much debugging time. To have your scripts give informative reports about errors that occur, use the mysqli_error() function. This function returns a textual version of the error that the MySQL server returned. It needs to be provided with the database connection: $dbc in this chapter: print mysqli_error($dbc); Connection errors are slightly different, however. To report upon those, invoke mysqli_connect_error(). This function does not take any arguments: print mysqli_connect_error(); Along with these functions, you may want to use some PHP tools for handling errors. For beginners, you can start with the error suppression operator (@). When used preceding a function name, it suppresses any error messages or warnings the function might invoke: @function_name(); 352 Chapter 12 Database Permissions Database permissions are a bit more complicated than file permissions, but you need to understand this: Different types of users can be assigned different database capabilities. For example, one DBMS user may be able to create new databases and delete existing ones (you may have dozens of databases in your DBMS), but a lower-level user may only be able to create and modify tables within a single database. The most basic user may just be able to read from, but not modify, tables. If you’re using PHP and MySQL for a live hosted site, the hosting company will most likely give you the second type of access—control over a single database but not the DBMS itself—and establish the initial database for you. If you’re working on your own server or have administrative access, you should have the capability to create new users and databases. Script 12.2 By adding error control to the script (the @ symbol and the mysqli_error() function), you can more purposefully address problems that occur. 1 2 3 4 5 6 7 8 9 10 11 12 Connect to MySQL Successfully connected to the database!

'; 15 16 17 18 19 20 21 22 23 24 25 26 mysqli_close($dbc); // Close the connection. } else { rint '

Could not connect to the database:
' . mysqli_connect_ error() . '.

'; } ?> Note that this operator doesn’t stop the error from happening; it just prevents the message from being immediately displayed. You’d use it in situations where you intend to handle the error yourself, should one occur. This is an important point: The error still happens, so you should use the error suppression operator only when you’re handling the error in another way. To use error handling: 1. Open mysqli_connect.php (Script 12.1) in your text editor or IDE. 2. Suppress any PHP errors created by the mysqli_connect() function by changing the if conditional as follows (Script 12.2): if ($dbc = @mysqli_connect ➝ ('localhost', 'username', ➝ 'password', 'myblog')) { Rather than have PHP print out an error message when the mysqli_connect() function backfires (B in the previous section, “Connecting to MySQL”), the message will be suppressed here using the @ symbol. The errors still occur, but they’re handled by the change made in the next step. 3. Add the mysqli_error() function to the print statement in the else section: print '

Could not connect to ➝ MySQL:
' . mysqli_connect_ ➝ error() . '.

'; continues on next page Intro to Databases 353 Instead of printing a message or relying on whatever error PHP kicks out (see B in the previous section, “Connecting to MySQL”), the script now prints the MySQL error within this context. You accomplish this by printing some HTML concatenated with the mysqli_connect_error() function. You should note that the mysqli_connect_error() function is not provided with the database connection—$dbc—as an argument, since no database connection was made. 4. Save the file, and test it again in your browser A. If there was a problem, this result now looks better than what would have been shown previously. If the script connected, the result is like that shown in A in the previous section, “Connecting to MySQL,” because neither of the error-management tools is involved. In this chapter, error messages are revealed to assist in the debugging process. Live websites should not have this level of explicit error messages shown to the user. The error suppression operator should be used only in very limited situations— namely, when you’re handling the error in other ways. As you build your PHP skills, you’ll learn more sophisticated approaches for error management, such as using exceptions and writing your own error handler. You may also see code where die(), which is an alias for exit(), is called when a connection error occurs. The thinking is that since a database connection cannot be made, there’s no point in continuing. In my opinion, that’s too heavy-handed an approach. 354 Chapter 12 A Using PHP’s error-control functions, you can adjust how errors are handled. Creating a Table Once you’ve created and selected the initial database, you can begin creating individual tables in it. A database can consist of multiple tables, but in this simple example you’ll create one table in which all the chapter’s data will be stored. To create a table in the database, you’ll use SQL—the language that databases understand. Because SQL is a lot like spoken English, the proper query to create a new table reads like this: CREATE TABLE tablename (column1 ➝ definition, column2 definition, ➝ etc.) For each column, separated by commas, you first indicate the column name and then the column type. Common types are TEXT, VARCHAR (a variable number of characters), DATETIME, and INT (integer). Because it’s highly recommended that you create a column that acts as the primary key (a column used to refer to each row), a simple CREATE statement could be CREATE TABLE my_table ( id INT PRIMARY KEY, information TEXT ) A table’s primary key is a special column of unique values that is used to refer to the table’s rows. The database makes an index of this column in order to more quickly navigate through the table. A table can have only one primary key, which you normally set up as an automatically incremented column of integers. The first row has a key of 1, the second has a key of 2, and so forth. Referring back to the key always retrieves the values for that row. Intro to Databases 355 Finally, it’s a good idea to establish the default character set when creating a table (or a database). This is accomplished by adding CHARACTER SET name at the end of the table creation statement: CREATE TABLE my_table ( id INT PRIMARY KEY, information TEXT ) CHARACTER SET utf8 Like the charset meta tag in HTML, this is merely an indication of what encoding to use for the stored characters. You almost certainly want to use utf8 here. You can visit the MySQL website for more information on SQL, column definitions, and character sets. By following the directions in this section, though, you should be able to accomplish some basic database tasks. The table that you’ll create in this example is represented by Table 12.2. In this example, you’ll create the database table that will be used to store information submitted via an HTML form. In the next section of the chapter, you’ll write the script that inserts the submitted data into the table created here. To create the table with PHP, you use the mysqli_query() function to execute a CREATE TABLE SQL command: mysqli_query($dbc, 'CREATE TABLE ➝ entries...'); Alternatively, you can execute that same SQL command via another interface, such as the command-line MySQL client or the web-based phpMyAdmin. 356 Chapter 12 TABLE 12.1 The ENTRIES Table Column Name Column Type id Positive, non-null, automatically incrementing integer Title Text up to 100 characters in length Entry Text of any length date_entered A timestamp including both the date and the time the row was added Script 12.3 To create a database table, define the appropriate SQL statement and then invoke the mysqli_query() function. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Create a Table The table has been created!

'; } else { print '

Could not create the table because:
' . mysqli_ error($dbc) . '.

The query being run was: ' . $query . '

'; } mysqli_close($dbc); // Close the connection. } else { // Connection failure. print '

Could not connect to the database:
' . mysqli_connect_error() . '.

'; } ?> To create a new table: 1. Begin a new PHP document in your text editor or IDE, to be named create_table.php (Script 12.3): Create a Table 2. Begin a section of PHP code: The table has been ➝ created.

'; } else { print '

Could not create the ➝ table because:
' . mysqli_ ➝ error($dbc) . '.

The ➝ query being run was: ' . ➝ $query . '

'; } To create the table, call the mysqli_query() function using the database connection as the first argument and the query variable—$query— as the second. If a problem occurred, the MySQL error is printed, along with the value of the $query variable. This last step—printing the actual query being executed—is a particularly useful debugging technique A. A If the query caused an error, the MySQL error will be reported and the query itself displayed (for debugging purposes). 358 Chapter 12 6. Close the database connection, and complete the $dbc conditional: B If all went well, all you’ll see is this message. mysqli_close($dbc); } else { // Connection failure. print '

Could not connect to ➝ the database:
' . mysqli_ ➝ connect_error() . '.

'; 7. Complete the PHP code and the HTML page: ?> 8. Save the script as create_table.php, place it in the proper directory for your PHP-enabled server, and test it in your browser B. It’s not necessary to write your SQL keywords in all capital letters as I do here, but doing so helps distinguish the SQL terms from the table and column names. On larger web applications, I highly recommended that you place the database connection code in a separate file, located outside the web directory. Then, each page that requires the database can include this external file. You’ll see an example of this in Chapter 13, “Putting It All Together.” The mysqli_query() function returns TRUE if a query was successfully run on a database. That result doesn’t necessarily mean the desired result occurred. This chapter presents the basics of MySQL- and SQL-related knowledge (including column types). You’ll want to check out other resources—listed in Appendix B—once you’re comfortable with the fundamentals. You wouldn’t normally use a PHP script to create a table, just as you wouldn’t normally create a database using a PHP script, but when you’re just starting with MySQL, this is an easy way to achieve the desired results. Intro to Databases 359 Inserting Data into a Database As mentioned, this database will be used as a simple blog, an online journal. Blog entries—consisting of a title and text—will be added to the database using one page and then displayed on another page. The last script created the table, which consists of four columns: id, title, entry, and date_entered. The process of adding information to a table is similar to creating the table itself in terms of which PHP functions you use, but the SQL query is different. To insert records, use the INSERT SQL command with either of the following syntaxes: INSERT INTO tablename VALUES ➝ (value1, value2, value3, etc.) INSERT INTO tablename ➝ (column1_name, column2_name) ➝ VALUES (value1, value2) The query begins with INSERT INTO tablename. Then you can either specify which columns you’re inserting values for or not name the columns explicitly. The former is more specific and is therefore preferred, but it can be tedious if you’re populating a slew of columns. In either case, you must be certain to list the right number of total values and the right type of value for each column. The values are placed within parentheses, with each value separated by a comma. Non-numeric values—strings and dates— need to be quoted, whereas numbers do not: INSERT INTO example (name, age) ➝ VALUES ('Jonah', 1) The query is executed using the mysqli_query() function. Because INSERT queries can be complex, it makes sense to assign each query to a variable and send that variable to the mysqli_query() function (as previously demonstrated). To demonstrate, let’s create a page that adds blog entries to the database. Like many of the examples in the preceding chapter, this one will both display and handle the HTML form. Before getting into the example, though, I’ll say that this script knowingly has a security hole in it; it’ll be explained and fixed in the next section of the chapter. Building on This Example The focus in this chapter is on explaining and demonstrating the basics of using PHP with MySQL. This also includes the core components of SQL. However, this chapter’s examples do a few things that you wouldn’t want to do in a real site, such as allow anyone to insert, edit, and delete database records. In the next chapter, a different example will be developed that is also database driven. That example will use cookies to restrict what users can do with the site. 360 Chapter 12 To enter data into a database from an HTML form: 1. Begin a new PHP document in your text editor or IDE, to be named add_entry.php (Script 12.4): Add a Blog Entry

Add a Blog Entry

continues on next page Script 12.4 The query statement for adding information to a database is straightforward enough, but be sure to match the number of values in parentheses to the number of columns in the database table. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Add a Blog Entry

Add a Blog Entry

Please submit both a title and an entry.

'; $problem = TRUE; } if (!$problem) { // Connect and select: $dbc = mysqli_connect('localhost', 'username', 'password', 'myblog'); code continues on next page Intro to Databases 361 2. Create the initial PHP section, and check for the form submission: Please submit both a ➝ title and an entry.

'; $problem = TRUE; } Before you use the form data in an INSERT query, it ought to be validated. Just a minimum of validation is used here, guaranteeing that some values are provided. If so, new variables are assigned those values, after trimming away extraneous spaces and applying strip_tags() (to prevent cross-site scripting attacks and other potential problems). If either of the values was empty, an error message is printed A, and the $problem flag variable is set to TRUE (because there is a problem). Script 12.4 continued 29 30 // Define the query: query = "INSERT INTO entries (id, title, entry, date_entered) VALUES (0, $ '$title', '$entry', NOW())"; 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 // Execute the query: f (@mysqli_query($dbc, $query)) { i print '

The blog entry has been added!

'; } else { print '

Could not add the entry because:
' . mysqli_ error($dbc) . '.

The query being run was: ' . $query . '

'; } mysqli_close($dbc); // Close the connection. } // No problem! } // End of form submission IF. // Display the form: ?> 362 Chapter 12 4. Connect to the database: if (!$problem) { $dbc = mysqli_connect ➝ ('localhost', 'username', ➝ 'password', 'myblog'); A The PHP script performs some basic form validation so that empty records are not inserted into the database. Having basically valid data, it’s safe to add the record to the database, so a connection must be established. At this point, if you’re running these examples in order, I’ll assume you have a working connection and selection process down, so I’ll dispense with all the conditionals and error reporting (mostly to shorten the script). If you have problems connecting to and selecting the database, apply the code already outlined in the chapter. 5. Define the INSERT query: $query = "INSERT INTO entries ➝ (id, title, entry, date_ ➝ entered) VALUES (0, '$title', ➝ '$entry', NOW())"; The query begins with the necessary INSERT INTO tablename code. Then it lists the columns for which values will be submitted. After that is VALUES, followed by four values—one for each column, in order—separated by commas. When assigning this query to the $query variable, use double quotation marks so that the values of the variables will be automatically inserted by PHP. The $title and $entry variables are strings, so they must be placed within single quotation marks in the query itself. continues on next page Intro to Databases 363 Because the id column has been set to AUTO_INCREMENT, you can use 0 as the value and MySQL will automatically use the next logical value for that column. You can also use the special keyword NULL. To set the value of the date_entered column, use the MySQL NOW() function. It inserts the current time as that value. 6. Run the query on the database: if (@mysqli_query($dbc, $query)) { print '

The blog entry has ➝ been added!

'; } else { print '

Could not add the ➝ entry because:
' . ➝ mysqli_ error($dbc) . '. ➝

The query being run ➝ was: ' . $query . '

'; } The query, once defined, is run using the mysqli_query() function. By calling this function as the condition of an if-else statement, you can print simple messages indicating the result of the query execution. As an essential debugging tool, if the query didn’t run properly, the MySQL error and the query being run are both printed to the browser B. 7. Close the database connection, the $problem conditional, and complete the main conditional and the PHP section: mysqli_close($dbc); } // No problem! } // End of form submission IF. ?> From here on out, the form will be displayed. 8. Create the form: B If the INSERT query didn’t work, the MySQL error is printed out along with the query that was run. 364 Chapter 12 The HTML form is very simple, requiring only a title for the blog entry and the entry itself. As a good rule of thumb, use the same name for your form inputs as for the corresponding column names in the database. Doing so makes errors less likely. 9. Finish the HTML page: C This is the form for adding an entry to the database. 10. Save the script as add_entry.php, place it in the proper directory for your PHP-enabled server, and test it in your browser C and D. You should probably avoid using apostrophes in your form values or you might see results like those in B. You’ll find the explanation and solution in the next section. To retrieve the automatically incremented number created for an AUTO_INCREMENT column, call the mysqli_insert_id() function. Because of the way auto-incrementing primary keys work, this query is also fine: D If the INSERT query ran properly, a message is printed and the form is displayed again. INSERT INTO entries (title, entry, ➝ date_entered) VALUES ('$title', ➝ '$entry', NOW())"; MySQL allows you to insert several records at once, using this format: INSERT INTO tablename ➝ (column1_name, column2_name) ➝ VALUES (value1, value2), (value3, ➝ value4); Most other database applications don’t support this construct, though. Intro to Databases 365 Securing Query Data as the blog post title, the resulting query would be As I mentioned in the introduction to the section “Inserting Data into a Database,” the code as written has a pretty bad security hole in it. As it stands, if someone submits text that contains an apostrophe, that data will break the SQL query A (security concerns aside, it’s also a pretty bad bug). The result is obviously undesirable, but why is it insecure? INSERT INTO entries ➝ (id, title, entry, date_entered) ➝ VALUES (0, '';DROP TABLE ➝ entries;', '', NOW()) If malicious users know they can break a query by typing an apostrophe, they may try to run their own queries using this hole. If someone submitted ‘;DROP TABLE entries; The initial apostrophe in the provided entry title has the effect of completing the blog title value part of the query. The semicolon then terminates the INSERT query itself. This will make the original query syntactically invalid. Then the database will be provided with a second query—DROP TABLE entries—with the hope that it will be executed when the original INSERT query fails. A The poor handling of apostrophes allows users to break the query because apostrophes (or single quotation marks) are used to delimit strings used in queries. 366 Chapter 12 This is known as an SQL injection attack, but fortunately it’s easy to prevent. To do so, send potentially insecure data to be used in a query through the mysqli_real_escape_string() function. This function will escape—preface with a backslash—any potentially harmful characters, making the data safe to use in a query: $var = mysqli_real_escape_string ➝ ($dbc, $var); For this function to work properly, the character set needs to be established for the communications: mysqli_set_charset($dbc, 'utf8') This code effectively serves the same purpose as the charset meta tag in HTML: indicating the character set—or character encoding—of the data to follow. The previous code does assume your PHP script, database, and table are all using UTF-8, which they really ought to be by default (and was specifically established on the table when it was created, just to be certain). Showing MySQL Errors Even if MySQL doesn’t execute an injected SQL command (normally MySQL will only run a single SQL query sent through the mysqli_query() function), hackers will provide bad characters in form data in the hopes that the syntactically broken query generates a database error. By seeing the database error, the hacker seeks to gain knowledge about the database that can be used for malicious purposes. For this reason, it’s imperative that a live site never reveal the actual MySQL errors or queries being executed. The scripts in this chapter do so only for your own debugging purposes. Let’s apply this function to the preceding script. Because both mysqli_real_escape_string() and mysqli_set_charset() require the data- base connection, the logic of the script must be tweaked a bit. Intro to Databases 367 To secure query data: 1. Open add_entry.php (Script 12.4) in your text editor or IDE, if it is not already open. 2. Update the assignment of the $title and $entry variables to read (Script 12.5) as follows: $title = mysqli_real_escape_ ➝ string($dbc, trim(strip_tags ➝ ($_POST['title']))); $entry = mysqli_real_escape_ ➝ string($dbc, trim(strip_tags ➝ ($_POST['entry']))); These two lines will greatly improve the security and functionality of the script. For both posted variables, their values are first trimmed and stripped of tags, then sent through mysqli_real_ escape_string(). The result will be safe to use in the query. If the application of three functions to one variable is too confusing for you, you can separate the code into discrete steps: $title = $_POST['title']; $title = trim(strip_tags ➝ ($title)); $title = mysqli_real_escape_ ➝ string($dbc, $title); 3. Move the database connection code— line 27 in Script 12.4—to above the validation lines. The database connection should be established within the form handling code, but before $problem = FALSE;. continues on page 370 Script 12.5 To better secure the web application and the database, the mysqli_real_escape_string() function is applied to the form data used in the query. 1 2 3 4 5 6 7 8 9 10 11 12 13 Add a Blog Entry

Add a Blog Entry

Please submit both a title and an entry.

'; $problem = TRUE; } if (!$problem) { // Define the query: $query = "INSERT INTO entries (id, title, entry, date_entered) VALUES (0, '$title', '$entry', NOW())"; // Execute the query: if (@mysqli_query($dbc, $query)) { print '

The blog entry has been added!

'; } else { print '

Could not add the entry because:
' . mysqli_ error($dbc) . '.

The query being run was: ' . $query . '

'; } } // No problem! mysqli_close($dbc); // Close the connection. } // End of form submission IF. // Display the form: ?> Intro to Databases 369 4. Move the database closing code— line 39 in Script 12.4—to just before the close of the form submission conditional. Because the database connection is opened first thing within the form handling conditional, the database connection should be closed as the last step within that same block. 5. After opening the database connection, identify the character set in use: mysqli_set_charset($dbc, 'utf8'); B Now apostrophes in form data… This needs to be done before mysqli_real_escape_string() is invoked. 6. Save the script, place it on your PHPenabled server, and test it in your browser B and C. PHP’s addslashes() function works similarly to mysqli_real_escape_string() but is not nearly as secure. 370 Chapter 12 C …will not cause problems. Retrieving Data from a Database The next process this chapter demonstrates is retrieving data from a populated table. You still use the mysqli_query() function to run the query, but retrieving data is slightly different than inserting data—you have to assign the query result to a variable and then use another function to fetch the data. The basic syntax for retrieving data is the SELECT query: SELECT what columns FROM what table The easiest query for reading data from a table is SELECT * FROM tablename The asterisk is the equivalent of saying every column. If you require only certain columns to be returned, you can limit your query, like so: SELECT name, email FROM users That query requests that only the information from two columns—name and email—be gathered. Keep in mind that this structure doesn’t limit what rows (or records) are returned, just what columns for those rows. Another way to alter your query is to add a conditional restricting which rows are returned, accomplished using a WHERE clause: SELECT * FROM users WHERE name= ➝ 'Larry' Here you want the information from every column in the table, but only from the rows where the name column is equal to Larry. This is a good example of how SQL uses only a few terms effectively and flexibly. The main difference in retrieving data from a database as opposed to inserting data into a database is that you need to handle the query differently. You should first assign the results of the query to a variable: $result = mysqli_query($dbc, ➝ $query); Just as $dbc is a reference to an open database connection, $result is a reference to a query result set. This variable is then provided to the mysqli_fetch_ array() function, which retrieves the query results: $row = mysqli_fetch_array($result); The function fetches one row from the result set at a time, creating an array in the process. The array will use the selected column names as its indexes: $row['name'], $row['email'], and so on. As with any array, you must refer to the columns exactly as they’re defined in the database (the keys are case-sensitive). So, in this example, you must use $row['email'] instead of $row['Email']. If the query will return multiple rows, execute the mysqli_fetch_array() function within a loop to access them all: while ($row = mysqli_fetch_ ➝ array($result)) { // Do something with $row. } continues on next page Intro to Databases 371 With each iteration of the loop, the next row of information from the query (referenced by $result) is assigned to an array named $row. This process continues until no more rows of information are found. Within the loop, you would do whatever you want with $row. The best way to understand this new code is to try it. You’ll write a script that retrieves the posts stored in the entries table and displays them A. You may want to run through add_entry.php a couple of more times to build up the table first. A This dynamic web page uses PHP to pull data from a database. To retrieve data from a table: 1. Begin a new PHP document in your text editor or IDE, to be named view_entries.php (Script 12.6): View My Blog

My Blog

Script 12.6 The SQL query for retrieving all data from a table is quite simple, but in order for PHP to access every returned record, you must loop through the results one row at a time. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 View My Blog

My Blog

{$row['title']}

{$row['entry']}
Edit Delete

\n"; } } else { // Query didn't run. print '

Could not retrieve the data because:
' . mysqli_ error($dbc) . '.

The query being run was: ' . $query . '

'; } // End of query IF. mysqli_close($dbc); // Close the connection. ?> Intro to Databases 373 5. Print out the returned results: while ($row = mysqli_fetch_ ➝ array($r)) { print "

{$row['title']} ➝

{$row['entry']}
Edit Delete

\n"; } This loop sets the variable $row to an array containing the first record returned in $r. The loop then executes the following command (the print statement). Once the loop gets back to the beginning, it assigns the next row, if it exists. It continues to do this until there are no more rows of information to be obtained. Within the loop, the array’s keys are the names of the columns from the table— hence, id, title, and entry (it’s not printing out the date_entered). At the bottom of each post, two links are created: to edit_entry.php and delete_entry.php. These scripts will be written in the rest of the chapter. Each link passes the posting’s database ID value along in the URL. That information will be necessary for those other two pages to edit and delete the blog posting accordingly. 374 Chapter 12 B Thanks to the SELECT query, which orders the returned records by the date they were entered, the most recently added entry is always listed first. 6. Handle the errors if the query didn’t run: } else { // Query didn't run. print '

➝ Could not retrieve the ➝ data because:
' . ➝ mysqli_error($dbc) . '. ➝

The query being run ➝ was: ' . $query . '

'; } // End of query IF. If the query couldn’t run on the database, it should be printed out, along with the MySQL error (for debugging purposes). 7. Close the database connection: mysqli_close($dbc); 8. Complete the PHP section and the HTML page: ?> 9. Save the script as view_entries.php, place it in the proper directory for your PHP-enabled server, and test it in your browser A. 10. If you want, add another record to the blog using the add_entry.php page (Script 12.6), and run this page again B. 11. Check the source code of the page to see the dynamically generated links C. The mysqli_fetch_array() function takes another argument, which is a constant indicating what kind of array should be returned. MYSQLI_ASSOC returns an associative array, whereas MYSQLI_NUM returns a numerically indexed array. The mysqli_num_rows() function returns the number of records returned by a SELECT query. It’s possible to paginate returned records so that 10 or 20 appear on each page (like the way Google works). Doing so requires more advanced coding than can be taught in this book, though. See my book PHP and MySQL for Dynamic Web Sites: Visual QuickPro Guide (Peachpit Press, 2012), or look online for code examples and tutorials. C Part of the HTML source of the page. Note that the two links have ?id=X appended to each URL. Intro to Databases 375 Deleting Data in a Database Sometimes you might also want to run a DELETE query on a database. Such a query removes records from the database. The syntax for a delete query is DELETE FROM tablename WHERE ➝ column=value The WHERE clause isn’t required, but if it’s omitted, you’ll remove every record from the table. You should also understand that once you delete a record, there’s no way to recover it (unless you have a backup of the database). As a safeguard, if you want to delete only a single record from a table, add the LIMIT clause to the query: A When the user arrives at this page, the blog entry is shown, and the user must confirm deleting it. DELETE FROM tablename WHERE ➝ column=value LIMIT 1 This clause ensures that only one record is deleted at most. Once you’ve defined your query, it’s again executed using the mysqli_query() function, like any other query. To see if a DELETE query worked, you can use the mysqli_affected_rows() function. This function returns the number of rows affected by an INSERT, DELETE, or UPDATE query. It takes the database connection as an argument. As an example, let’s write the delete_ entry.php script, which is linked from the view_blog.php page. This page receives the database record ID in the URL. It then displays the entry to confirm that the user wants to delete it A. If the user clicks the button, the record will be deleted B. 376 Chapter 12 B If the delete query worked properly, the user sees this result. To delete data from a database: 1. Begin a new PHP document in your text editor or IDE, to be named delete_entry.php (Script 12.7): Delete a Blog Entry ➝

Delete an Entry

2. Start the PHP code, and connect to the database: Delete a Blog Entry

Delete an Entry

Are you sure you want to delete this entry?

' . $row['title'] . '

' . $row['entry'] . '

'; } else { // Couldn't get the information. print '

Could not retrieve the blog entry because:
' . mysqli_ error($dbc) . '.

The query being run was: ' . $query . '

'; } } elseif (isset($_POST['id']) && is_numeric($_POST['id'])) { // Handle the form. // Define the query: query = "DELETE FROM entries WHERE id={$_POST['id']} LIMIT 1"; $ $r = mysqli_query($dbc, $query); // Execute the query. // Report on the result: f (mysqli_affected_rows($dbc) == 1) { i print '

The blog entry has been deleted.

'; } else { print '

Could not delete the blog entry because:
' . mysqli_error($dbc) . '.

The query being run was: ' . $query . '

'; } } else { // No ID received. print '

This page has been accessed in error.

'; } // End of main IF. mysqli_close($dbc); // Close the connection. ?> Chapter 12 3. If the page received a valid entry ID in the URL, define and execute a SELECT query: if (isset($_GET['id']) && is_ ➝ numeric ($_GET['id']) ) { $query = "SELECT title, ➝ entry FROM entries WHERE ➝ id={$_GET['id']}"; if ($r = mysqli_query($dbc, ➝ $query)) { To display the blog entry, the page must confirm that a numeric ID is received by the page. Because that value should first come in the URL (when the user clicks the link in view_blog.php, see C in the previous section, “Retrieving Data from a Database”), you reference $_GET['id']. The use of is_numeric() here does more than just ensure a record can be retrieved; it’s also an important security measure. Because the $_GET['id'] value is used directly in the query—without quotes—testing that value against is_numeric() prevents the query from breaking or being used in an attack. The query is like the SELECT query used in the preceding example, except that the WHERE clause has been added to retrieve a specific record. Also, because only the two stored values are necessary—the title and the entry itself—only those are being selected. This query is then executed using the mysqli_query() function. 4. Retrieve the record, and display the entry in a form: $row = mysqli_fetch_array($r); print ''; Instead of retrieving all the records using a while loop, as you did in the previous example, use one call to the mysqli_fetch_array() function to assign the returned record to the $row variable. Using this array, the record to be deleted can be displayed. The form first shows the blog entry details, much as it did in the view_entries.php script. When the user clicks the button, the form will be submitted back to this page, at which point the record should be deleted. In order to do so, the blog identification number, which is passed to the script as $_GET['id'], must be stored in a hidden input so that it exists in the $_POST array upon submission (because $_GET['id'] won’t have a value at that point). continues on next page Intro to Databases 379 5. Report an error if the query failed: } else { // Couldn't get the ➝ information. print '

➝ Could not retrieve the blog ➝ entry because:
' . mysqli_ ➝ error($dbc) . '.

The ➝ query being run was: ' . $query . '

'; } If the SELECT query failed to run, the MySQL error and the query itself are printed out. 6. Check for the submission of the form: } elseif (isset($_POST['id']) && ➝ is_numeric($_POST['id'])) { // ➝ Handle the form. This elseif clause is part of the conditional begun in Step 3. It corresponds to the second usage of this same script (the form being submitted). If this conditional is TRUE, the record should be deleted. 7. Define and execute the query: $query = "DELETE FROM entries ➝ WHERE id={$_POST['id']} LIMIT ➝ 1"; $r = mysqli_query($dbc, $query); This query deletes the record whose id has a value of $_POST['id']. The ID value comes from the form, where it’s stored as a hidden input. By adding the LIMIT 1 clause to the query, you can guarantee that only one record, at most, is removed. 380 Chapter 12 8. Check the result of the query: if (mysqli_affected_rows($dbc) ➝ == 1) { print '

The blog entry has ➝ been deleted.

'; } else { print '

➝ Could not delete the blog ➝ entry because:
' . mysqli_ ➝ error($dbc) . '.

The ➝ query being run was: ' . ➝ $query . '

'; } The mysqli_affected_rows() function returns the number of rows altered by the most recent query. If the query ran properly, one row was deleted, so this function should return 1. If so, a message is printed. Otherwise, the MySQL error and query are printed for debugging purposes. 9. Complete the main conditional: } else { // No ID received. print '

➝ This page has been accessed ➝ in error.

'; } // End of main IF. If no numeric ID value was passed to this page using either the GET method or the POST method, then this else clause takes effect C. 10. Close the database connection, and complete the page: mysqli_close($dbc); ?> C If the script does not receive an id value in the URL, an error is reported. 11. Save the script as delete_entry.php, place it in the proper directory for your PHP-enabled server, and test it in your browser A and B. To test this script, you must first run view_entries.php. Then, click one of the Delete links to access delete_entry.php. You can empty a table of all of its records by running the query TRUNCATE TABLE tablename. This approach is preferred over using DELETE FROM tablename. TRUNCATE will completely drop and rebuild the table, which is better for the database. It’s a fairly common error to try to run the query DELETE * FROM tablename, like a SELECT query. Remember that DELETE doesn’t use the same syntax as SELECT, because you aren’t deleting specific columns. Intro to Databases 381 Updating Data in a Database The final type of query this chapter will cover is UPDATE. It’s used to alter the values of a record’s columns. The syntax is UPDATE tablename SET ➝ column1_name=value, ➝ column2_name=value2 WHERE ➝ some_column=value As with any other query, if the values are strings, they should be placed within single quotation marks: UPDATE users SET first_name= ➝ 'Eleanor', age=7 WHERE user_id=142 A When the user arrives at the edit page, the form is shown with the existing values. As with a DELETE query, you should use a WHERE clause to limit the rows that are affected. If you don’t do this, every record in the database will be updated. To test that an update worked, you can again use the mysqli_affected_rows() function to return the number of records altered. To demonstrate, let’s write a page for editing a blog entry. It will let the user alter an entry’s title and text, but not the date entered or the blog ID number (as a primary key, the ID number should never be changed). This script will use a structure like that in delete_entry.php (Script 12.7), first showing the entry A and then handling the submission of that form B. 382 Chapter 12 B Upon submitting the form, the user sees a message like this. To update data in a database: 1. Begin a new PHP document in your text editor or IDE, to be named edit_entry.php (Script 12.8). Edit a Blog Entry</ ➝ title> </head> <body> <h1>Edit an Entry</h1> 2. Start your PHP code and connect to the database: <?php // Script 12.8 ➝ edit_entry.php $dbc = mysqli_connect ➝ ('localhost', 'username', ➝ 'password', 'myblog'); mysqli_set_charset($dbc, 'utf8'); Because this script uses the mysqli_ real_escape_string() function, it also needs to set the character set (which you can do for all the scripts, if you want to be consistent). continues on page 385 Script 12.8 You can edit records in a database table by using an UPDATE SQL command. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 <!doctype html> <html lang="en"> <head> <meta charset="utf-8"> <title>Edit a Blog Entry

Edit an Entry

Entry Title:

Entry Text: ' . htmlentities($row['entry']) . '

'; } else { // Couldn't get the information. print '

Could not retrieve the blog entry because:
' . mysqli_error($dbc) . '.

The query being run was: ' . $query . '

'; } } elseif (isset($_POST['id']) && is_numeric($_POST['id'])) { // Handle the form. // Validate and secure the form data: $problem = FALSE; if (!empty($_POST['title']) && !empty($_POST['entry'])) { $title = mysqli_real_escape_string($dbc, trim(strip_tags($_POST['title']))); $entry = mysqli_real_escape_string($dbc, trim(strip_tags($_POST['entry']))); } else { print '

Please submit both a title and an entry.

'; $problem = TRUE; } if (!$problem) { // Define the query. query = "UPDATE entries SET title='$title', entry='$entry' WHERE $ id={$_POST['id']}"; $r = mysqli_query($dbc, $query); // Execute the query. // Report on the result: if (mysqli_affected_rows($dbc) == 1) { print '

The blog entry has been updated.

'; } else { print '

Could not update the entry because:
' . mysqli_error($dbc) . '.

The query being run was: ' . $query . '

'; } } // No problem! } else { // No ID set. print '

This page has been accessed in error.

'; } // End of main IF. mysqli_close($dbc); // Close the connection. ?> 384 Chapter 12 3. If the page received a valid entry ID in the URL, define and execute a SELECT query: if (isset($_GET['id']) && ➝ is_numeric($_GET['id']) ) { $query = "SELECT title, ➝ entry FROM entries WHERE ➝ id={$_GET['id']}"; if ($r = mysqli_query($dbc, ➝ $query)) { This code is exactly the same as that in the delete page; it selects the two column values from the database for the provided ID value. 4. Retrieve the record, and display the entry in a form: $row = mysqli_fetch_array($r); print ''; Again, this is almost exactly the same as in the preceding script, including the most important step of storing the ID value in a hidden form input. Here, though, the stored data isn’t just printed but is actually used as the values for form elements. For security and to avoid potential conflicts, each value is run through htmlentities() first. 5. Report an error if the query failed: } else { // Couldn't get the ➝ information. print '

➝ Could not retrieve the blog ➝ entry because:
' . ➝ mysqli_error($dbc) . '. ➝

The query being run ➝ was: ' . $query . '

'; } 6. Check for the submission of the form: } elseif (isset($_POST['id']) && ➝ is_numeric($_POST['id'])) { This conditional will be TRUE when the form is submitted. 7. Validate and secure the form data: $problem = FALSE; if (!empty($_POST['title']) && ➝ !empty($_POST['entry'])) { $title = mysqli_real_escape_ ➝ string($dbc, trim(strip_tags ➝ ($_POST ['title']))); $entry = mysqli_real_escape_ ➝ string($dbc, trim(strip_tags ➝ ($_POST ['entry']))); } else { print '

➝ Please submit both a title ➝ and an entry.

'; $problem = TRUE; } This code comes from the page used to add blog postings. It performs minimal validation on the submitted data and then runs it through the mysqli_real_ escape_string() function to be safe. Because the form data can be edited, the form should be validated as if it were a new record being created. continues on next page Intro to Databases 385 8. Define and execute the query: if (!$problem) { $query = "UPDATE entries ➝ SET title='$title', ➝ entry='$entry' WHERE id= ➝ {$_POST['id']}"; $r = mysqli_query($dbc, ➝ $query); The UPDATE query sets the title column equal to the value entered in the form’s title input and sets the entry column equal to the value entered in the form’s entry text area. Only the record whose id is equal to $_POST['id'], which comes from a hidden form input, is updated. 9. Report on the success of the query: if (mysqli_affected_rows($dbc) ➝ == 1) { print '

The blog entry has ➝ been updated.

'; } else { print '

➝ Could not update the entry ➝ because:
' . mysqli_ error ➝ ($dbc) . '.

The query ➝ being run was: ' . $query . ➝ '

'; } If one row was affected, then a success message is returned. Otherwise, the 386 Chapter 12 MySQL error and the query are sent to the browser. 10. Complete the conditionals: } // No problem! } else { // No ID set. print '

➝ This page has been accessed ➝ in error.

'; } // End of main IF. If no numeric ID value was passed to this page using either the GET method or the POST method, then this else clause takes effect. 11. Close the database connection, and complete the page: mysqli_close($dbc); ?> 12. Save the file as edit_entry.php, place it in the proper directory for your PHP-enabled server, and test it in your browser A and B. As in the preceding example, to edit an entry, you must click its Edit link in the view_blog.php page. 13. Revisit view_blog.php to confirm that the changes were made C. C Reloading the view_blog.php script reflects the changes made to the entries. The id is a primary key, meaning that its value should never change. By using a primary key in your table, you can change every other value in the record but still refer to the row using that column. The mysqli_real_escape_string() function does not need to be applied to the ID values used in the queries, because the is_ numeric() test confirms they don’t contain apostrophes or other problematic characters. More thorough edit and delete pages would use the mysqli_num_rows() function in a conditional to confirm that the SELECT query returned a row prior to fetching it: if (mysqli_num_rows($r) == 1) {... If you run an update on a table but don’t change a record’s values, mysqli_ affected_rows() will return 0. It can’t hurt to add a LIMIT 1 clause to an UPDATE query, to ensure that only one row, at most, is affected. A common beginner’s mistake is to use the following erroneous syntax: UPDATE tablename SET column1_name= WHERE ➝ value AND column2_name=value2 ➝ some_column=value Note the improper AND in that example! Intro to Databases 387 Review and Pursue If you have any problems with the review questions or the pursue prompts, turn to the book’s supporting forum (www.LarryUllman.com/forums/). Pursue n n Review n n n n n n n What version of MySQL are you using? What values do you personally use to connect to MySQL? How does a PHP script connect to a MySQL server? How does it disconnect? What is the error suppression operator? What does it do? What function returns MySQLreported errors? What debugging techniques should you use when having problems with a PHP script that interacts with MySQL? What SQL command is used to create a table? To add new records? To retrieve records? To modify records? To remove records? What function should string values be run through to prevent SQL injection attacks? 388 Chapter 12 n n Find the version of the MySQL manual that corresponds to your version of MySQL. Start reading! Move the code for connecting to the database to a separate script, then include that script in the PHP pages that interact with the database. Don’t forget about setting the character set. Make the add_entry.php form sticky. Change the code in view_entries.php so that it converts newline characters in each entry into HTML break tags. 13 Putting It All Together The 12 chapters to this point have covered all the fundamentals of using PHP for web development. In this chapter, you’ll use your accumulated knowledge to create a complete and functional website. And even though the focus of this chapter is on applying your newfound knowledge, you’ll still learn a few new tricks. In particular, you’ll see how to develop a full-scale web application from scratch. In This Chapter Getting Started 390 Connecting to the Database 392 Writing the User-Defined Function 393 Creating the Template 396 Logging In 400 Logging Out 404 Adding Quotes 405 Listing Quotes 409 Editing Quotes 412 Deleting Quotes 418 Creating the Home Page 422 Review and Pursue 426 Getting Started The first step when starting any project is identifying the site’s goals. The primary goal of this chapter is to apply everything taught in the book thus far (a lofty aim, to be sure). The example for doing so combines ideas from the previous two chapters, creating a site that will store and display quotations. Instead of using a file to do so, as in Chapter 11, “Files and Directories,” this site will use a MySQL database as the storage repository. But as with the blog example from Chapter 12, “Intro to Databases,” the ability to create, edit, and delete quotations will be implemented. Further, the public user will be able to view the most recent quotation by default A, or a random one, or a random quotation previously marked as a favorite. For improved security, the site will have an administrator who can log in and log out. And only the logged-in administrator will be allowed to create, edit, or delete quotations B. A The site’s simple home page. 390 Chapter 13 The site will use a simple template to give every page a consistent look, with CSS handling all the formatting and layout. The site will also use one user-defined function, stored in an included file. As in Chapter 12, you must first create the database and its one table. You can do so using the instructions in Appendix A, “Installation and Configuration.” The database will be named myquotes (or something else if you’d rather). You create its one table with this SQL command: CREATE TABLE quotes ( id INT UNSIGNED NOT NULL ➝ AUTO_INCREMENT, quote TEXT NOT NULL, source VARCHAR(100) NOT NULL, favorite TINYINT(1) UNSIGNED NOT ➝ NULL, date_entered TIMESTAMP NOT NULL ➝ DEFAULT CURRENT_TIMESTAMP, PRIMARY KEY (id) ) CHARACTER SET utf8 B Nonadministrators are denied access to certain pages. The id is the primary key, and it will automatically be incremented to the next logical value with each new submission. The quote field stores the quote itself, with the source field storing the attribution (unlike in Chapter 11, where the quote and the source were stored together). The favorite field stores a 1 or a 0, marking the quote as a favorite or not. Finally, the date_entered column is a timestamp, automatically set to the current timestamp when a new record is created. Finally, a word about how the site should be organized on the server C. Ideally the mysqli_connect.php script, which establishes a database connection, would be stored outside the web root directory. If that is not possible in your case, you can place it in the includes folder, then change the code in the other scripts accordingly. You can create this table using a PHP script, such as Script 12.3, or a third-party application (like the MySQL client or phpMyAdmin). If you’d rather, you could move the templates and includes folders outside the web root directory as well. If so, you’ll need to change all the references to them in the code to reflect the alternative structure. Once you’ve created the database, the database table, and the necessary folders, you can begin coding. web root add_quote.php css style.css delete_quote.php mysql_connect.php edit_quote.php includes functions.php index.php login.php logout.php templates footer.html header.html view_quotes.php C The structure and organization of the files on the server. Putting It All Together 391 Connecting to the Database Unlike the scripts in Chapter 12, which connected to the database using code repeated in each script, this site will use the more common practice of placing the repeated code in a stand-alone file. Every script that interacts with the database— which will be most but not all of them—will then include this file. As you can see in C in the previous section, “Getting Started,” this file should be stored outside the web root directory or, if that’s not possible, within the includes folder. To create mysqli_connect.php: 1. B egin a new PHP script in your text editor or IDE, to be named mysqli_connect.php (Script 13.1): The header will start with a PHP section in order to include the functions.php script, which will be required by multiple pages on the site. The reference to the script is relative to the pages that will be including the header: files in the main directory. 396 Chapter 13 A If the person viewing any page is an administrator, additional links appear. 2. Begin the HTML document: Again, the style sheet needs to be downloaded from the book’s corresponding website. And the reference to that style sheet is relative to the scripts that include the header, all found within the main directory. 3. Print the page’s title: <?php if (defined('TITLE')) { print TITLE; } else { print 'My Site of Quotes'; } ?> This code also comes from Chapter 8, printing either the default title or a custom one, if set as a constant. 4. Complete the head: 5. Begin the page’s body:

My Site of Quotes

6. S ave the file as header.html, stored in the templates directory. Script 13.3 The header file includes the functions.php script and begins the HTML page. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 <?php // Print the page title. if (defined('TITLE')) { // Is the title defined? print TITLE; } else { // The title is not defined. print 'My Site of Quotes'; } ?>

My Site of Quotes

Putting It All Together 397 To create footer.html: 1. B egin a new HTML document in your text editor or IDE, to be named footer.html (Script 13.4): 2. C heck if it’s appropriate to display general administration links:

Site Admin

Add Quote <-> View All Quotes <-> Logout

'; } ?> </div> 398 Chapter 13 The second part of the conditional, after the OR, checks if the $loggedin variable is set and has a TRUE value. This will be the case on the login.php page, after the user successfully logged in. The is_administrator() function won’t return a TRUE value at that juncture, because the cookie will have been just sent by the script and therefore won’t be available to be read. 3. Create the links: print '

Site Admin

➝

➝ Add Quote <-> ➝ View All Quotes <-> Logout ➝

'; Three links are created: to a page for adding new quotes, to a page for viewing every quote, and to the logout page. omplete the conditional and the 4. C PHP section: } ?> 5. Complete the HTML page:

6. S ave the file as footer.html, stored in the templates directory. Putting It All Together 399 Logging In Next, it’s time to create the script through which the administrator can log in. The result will be very similar to the scripts in Chapter 9, “Cookies and Sessions,” with one structural difference: That chapter used output buffering, allowing you to lay out your script however you want. This site does not use output buffering, so the handling of the form must be written in such a way that the cookie can be sent without generating headers already sent errors (see Chapter 9 if this isn’t ringing a bell for you). In other words, the script must check for a form submission prior to including the header. To still be able to reflect errors and other messages within the context of the page, you must use variables. To create login.php: 1. B egin a new PHP document in your text editor or IDE, to be named login.php (Script 13.5): ' . $error . '

'; } // Indicate the user is logged in, or show the form: if ($loggedin) { print '

You are now logged in!

'; } else { print '

Login Form

'; } include('templates/footer.html'); // Need the footer. ?> Putting It All Together 401 7. C reate error messages for the two other conditions: } else { // Incorrect! $error = 'The submitted ➝ email address and ➝ password do not match ➝ those on file!'; } } else { // Forgot a field. $error = 'Please make sure ➝ you enter both an email ➝ address and a password!'; } } The first else clause applies if an email address and password were provided but were wrong. The second else clause applies if no email address or password was submitted. In both cases, the message is assigned to a variable so that it may be used later in the script. et the page title, and include the 8. S header file: define('TITLE', 'Login'); include('templates/header.html'); 9. Print an error if one exists: if ($error) { print '

' . ➝ $error . '

'; } The error itself will be determined in Step 7, but it can’t be printed at that point because the HTML header will not have been included. The solution is to have this code check for a non-FALSE $error value and then print $error within some HTML and CSS A. 402 Chapter 13 A Error messages are displayed after the header is included but before the HTML form. 10. Indicate that the user is logged in, or display the form: B The result upon successfully logging in. C The basic login form. if ($loggedin) { print '

You are now logged ➝ in!

'; } else { print '

Login Form

'; } If the $loggedin variable has a TRUE value—its value is FALSE by default— then the user just successfully logged in to the site and a message saying so is displayed B. If the $loggedin variable still has its default value, then the form should be shown C. 11. Include the footer, and complete the page: include('templates/footer.html'); ?> 12. S ave the file as login.php. 13. Test the file in your browser (A, B, and C). I purposefully omitted creating a link to the login section (as a security measure), so you’ll need to enter the correct URL in your browser’s address bar. Note that, as written, the script requires administrators to log back in after an hour, whether or not they continue to be active in the site. Putting It All Together 403 Logging Out If you write a login process, there must be a logout process too. In this case, just using cookies, it’s a very simple script. To create logout.php: 1. B egin a new PHP document in your text editor or IDE, to be named logout.php (Script 13.6): You are now logged out.

'; // Include the footer: include('templates/footer.html'); ?> To delete the existing login cookie, another cookie is sent with the same name, a value of FALSE, and an expiration time in the past. 3. D efine a page title, and include the header: define('TITLE', 'Logout'); include('templates/header.html'); 4. Print a message: print '

You are now logged ➝ out.

'; 5. Include the footer: include('templates/footer.html'); ?> 6. Save the file as logout.php. 7. Test the file in your browser A. 404 Chapter 13 A The resulting logout page. Adding Quotes Now that the administrator has the ability to log in, she or he should be able to start adding quotations. The script for doing so is a lot like the one for adding blog postings (from Chapter 12), but the form will have an additional checkbox for marking the quotation as a favorite A. A The form for adding quotations to the database. Script 13.7 The add_quote.php script allows only administrators to add new quotations to the database. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Add a Quotation'; // Restrict access to administrators only: if (!is_administrator()) { print '

Access Denied!

You do not have permission to access this page.

'; include('templates/footer.html'); exit(); } // Check for a form submission: if ($_SERVER['REQUEST_METHOD'] == 'POST') { // Handle the form. if ( !empty($_POST['quote']) && !empty($_POST['source']) ) { Because this script creates records in the database, security must be a primary concern. As an initial precaution, the script will make sure that only the administrator can use the page. Second, values to be used in the SQL command will be sanctified to prevent invalid queries. To create add_quote.php: 1. B egin a new PHP document in your text editor or IDE, to be named add_quote.php (Script 13.7): Add a Quotation'; 2. D eny access to the page if the user is not an administrator: if (!is_administrator()) { print '

Access Denied! ➝

➝ You do not have permission to ➝ access this page.

'; include('templates/ ➝ footer.html'); exit(); } continues on next page 21 code continues on next page Putting It All Together 405 By invoking the is_administrator() function, the script can quickly test for that condition. If the user is not an administrator, an Access Denied error is displayed, the footer is included, and the script is terminated B. 3. Check for a form submission: if ($_SERVER['REQUEST_METHOD'] == ➝ 'POST') { B Any user not logged in as an administrator is denied access to the form. Note that this check comes after confirming that the user is an administrator. Script 13.7 continued 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 406 // Need the database connection: include('../mysqli_connect.php'); // Prepare the values for storing: $quote = mysqli_real_escape_string($dbc, trim(strip_tags($_POST['quote']))); $source = mysqli_real_escape_string($dbc, trim(strip_tags($_POST['source']))); // Create the "favorite" value: if (isset($_POST['favorite'])) { $favorite = 1; } else { $favorite = 0; } $query = "INSERT INTO quotes (quote, source, favorite) VALUES ('$quote', '$source', $favorite)"; mysqli_query($dbc, $query); if (mysqli_affected_rows($dbc) == 1){ // Print a message: print '

Your quotation has been stored.

'; } else { print '

Could not store the quote because:
' . mysqli_error($dbc) . '.

The query being run was: ' . $query . '

'; } // Close the connection: mysqli_close($dbc); } else { // Failed to enter a quotation. print '

Please enter a quotation and a source!

'; } } // End of submitted IF. Chapter 13 э 4. Check for values: if ( !empty($_POST['quote']) && ➝ !empty($_POST['source']) ) { This script performs a minimum of validation, checking that the two variables aren’t empty. With large blocks of text, such as a quotation, there’s not much more that can be done in terms of validation. 5. Prepare the values for use in the query: include('../mysqli_connect.php'); $quote = mysqli_real_escape_string ➝ ($dbc, trim(strip_tags($_POST ➝ ['quote']))); $source = mysqli_real_escape_string ➝ ($dbc, trim(strip_tags($_POST ➝ ['source']))); To make the two textual values safe to use in the query, they’re run through the mysqil_real_escape_string() function (see Chapter 12). Because this function requires a database connection, that file must first be included. To make the values safe to later display in the web page, the strip_tags() function is applied too (see Chapter 5, “Using Strings”). 6. Create the favorite value: if (isset($_POST['favorite'])) { $favorite = 1; } else { $favorite = 0; } In the database, a quotation’s status as a favorite is indicated by a 1. Nonfavorites are represented by a 0. To determine which number to use, all the PHP script has to do is check for a $_POST['favorite'] value. If that variable is set, regardless of what its value is, it means the user checked the favorite checkbox. If the user didn’t do that, then the variable won’t be set, and the $favorite variable will be assigned the value 0. 7. Define and execute the query: $query = "INSERT INTO quotes ➝ (quote, source, favorite) ➝ VALUES ('$quote', '$source', ➝ $favorite)"; mysqli_query($dbc, $query); The query specifies values for three fields and uses the variables already defined. The remaining two table columns—id and date_entered—will automatically be assigned values, thanks to the table’s definition. continues on next page Script 13.7 continued 55 56 57 58 59 60 61 62 63 64 65 // Leave PHP and display the form: ?> Putting It All Together 407 8. Print a message based on the results: if (mysqli_affected_rows($dbc) ➝ == 1){ // Print a message: print '

Your quotation has ➝ been stored.

'; } else { print '

➝ Could not store the quote ➝ because:
' . ➝ mysqli_error($dbc) . '. ➝

The query being run ➝ was: ' . $query . '

'; } If the INSERT query created one new row in the database, a message indicating that is displayed. Otherwise, debugging information is shown so that you can try to figure out what went wrong. 9. Complete the validation conditional: } else { // Failed to enter a ➝ quotation. print '

➝ Please enter a quotation and ➝ a source!

'; } 10. Complete the submission conditional and the PHP block: } // End of submitted IF. ?> 11. Create the form: The form has one text area, one text input, and a checkbox (plus the submit button, of course). It is not designed to be sticky—that’s a feature you could add later, if you wanted. 12. Include the footer: 13. Save the file as add_quote.php, and test in your browser C. The ability to create (INSERT), retrieve (SELECT), update, and delete database records is collectively referred to as CRUD. C The result after adding a quotation. 408 Chapter 13 Listing Quotes The administrative side of the site will have a page that lists every quote stored in the database A. Although the same script could easily be adapted for the public side, its primary purpose is to provide quick links for the administrator to edit or delete any quote (as opposed to searching randomly through the public side for the right quote to manage). A The full list of stored quotations, with links to edit or delete each. To create view_quotes.php: Script 13.8 This script lists every quotation currently stored, providing links for the administrator to edit or delete them. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Like the add_quote.php script, this page will restrict access to just administrators. All Quotes'; // Restrict access to administrators only: if (!is_administrator()) { print '

Access Denied!

You do not have permission to access this page.

'; include('templates/footer.html'); exit(); } // Need the database connection: include('../mysqli_connect.php'); // Define the query: $query = 'SELECT id, quote, source, favorite FROM quotes ORDER BY date_ entered DESC'; 22 code continues on next page 1. B egin a new PHP document in your text editor or IDE, to be named view_quotes.php (Script 13.8): All Quotes'; 2. T erminate the script if the user isn’t an administrator: if (!is_administrator()) { print '

Access Denied! ➝

You do ➝ not have permission to access ➝ this page.

'; include('templates/ ➝ footer.html'); exit(); } This is the exact same code as that in add_quote.php. Except for the browser’s title, the result for nonadministrators will be the same as in B in the previous section, “Adding Quotes.” continues on next page Putting It All Together 409 3. Include the database connection, and define the query: include('../mysqli_connect.php'); $query = 'SELECT id, quote, ➝ source, favorite FROM quotes ORDER BY date_entered DESC'; The query returns four columns—all but the date entered—from the database for every record. The results will be returned in order by the date they were entered. 4. E xecute the query, and begin retrieving the results: if ($r = mysqli_query ➝ ($dbc, $query)) { while ($row = ➝ mysqli_fetch_array($r)) { The while loop code was explained in Chapter 12, even though it wasn’t used in that chapter. This construct is how you fetch every record returned by a query. 5. Begin printing out the record: print "

➝ {$row['quote']}

➝ {$row['source']}\n"; This code starts a DIV, places the quotation itself within blockquote tags, and then shows the quote’s attribution. Script 13.8 continued 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 410 Chapter 13 // Run the query: if ($result = mysqli_query($dbc, $query)) { // Retrieve the returned records: while ($row = mysqli_fetch_ array($result)) { // Print the record: print "

{$row['quote']}- {$row['source']}\n"; // Is this a favorite? if ($row['favorite'] == 1) { print ' Favorite!'; } // Add administrative links: print "
Quote Admin: Edit <-> Delete

\n"; } // End of while loop. } else { // Query didn't run. print '
Could not retrieve the data because:
' . mysqli_error($dbc) . '.
The query being run was: ' . $query . ''; } // End of query IF. mysqli_close($dbc); // Close the connection. include('templates/footer.html'); // Include the footer. ?> 6. Indicate that the quotation is a favorite, if applicable: if ($row['favorite'] == 1) { print ' Favorite! ➝ '; } The value of $row['favorite'] will be either 1 or 0. If it’s 1, the word Favorite!, emphasized, is displayed along with the record. 7. A dd administrative links for editing and deleting the quote: print "
Quote Admin: ➝ Edit <-> Delete
➝

\n"; For each quote, two links must be created. The first is to edit_quote.php and the second to delete_quote.php. Each link must also pass the id value along in the URL, as the code in Chapter 12 does B. 8. Complete the while loop and the mysqli_query() conditional: } // End of while loop. } else { // Query didn't run. print '
➝ Could not retrieve the ➝ data because:
' . ➝ mysqli_error($dbc) . '. ➝
The query being run ➝ was: ' . $query . '
'; } // End of query IF. 9. Close the database connection: mysqli_close($dbc); 10. Complete the page: include('templates/footer.html'); ?> 11. S ave the view as view_quotes.php, and test in your browser. As some of the queries in this chapter demonstrate, you can use a column or value in an ORDER BY clause even if it’s not selected by the query. The end of the print statement closes the DIV for the specific quotation (begun in Step 5). B The HTML source code for the page shows how the id value is passed in the URL to the linked pages. Putting It All Together 411 Editing Quotes The view_quotes.php page (and later, index.php) has links to edit_quote.php, where the administrator can update a quote. Functionally, this script will be very similar to edit_entry.php from Chapter 12: 1. T he script needs to receive an ID value in the URL. 2. U sing the ID, the record is retrieved and used to populate a form A. 3. U pon form submission, the form data will be validated (even if only slightly). 4. If the form data passes validation, the record will be updated in the database. For the most part, this script is just another application of what you’ve already seen. But one new thing you’ll learn here is how to select or not select a form’s checkbox element based on a preexisting value. To create edit_quote.php: 1. B egin a new PHP document in your text editor or IDE, to be named edit_quote.php (Script 13.9): Edit a Quotation '; 2. T erminate the script if the user isn’t an administrator: if (!is_administrator()) { print '
Access Denied! ➝
You do ➝ not have permission to access ➝ this page.
'; include('templates/ ➝ footer.html'); exit(); } 412 Chapter 13 A The form’s elements are prepopulated, and preselected, using the record’s existing values. Script 13.9 The edit_quote.php script gives the administrator a way to update an existing record. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Edit a Quotation'; // Restrict access to administrators only: if (!is_administrator()) { print '
Access Denied!
You do not have permission to access this page.
'; include('templates/footer.html'); exit(); } // Need the database connection: include('../mysqli_connect.php'); if (isset($_GET['id']) && is_numeric($_ GET['id']) && ($_GET['id'] > 0) ) { // Display the entry in a form: 21 code continues on next page 3. Include the database connection: include('../mysqli_connect.php'); Both phases of the script—displaying the form and handling the form—require a database connection, so the included file is incorporated at this point. alidate that a numeric ID value was 4. V received in the URL: if (isset($_GET['id']) && ➝ is_numeric($_GET['id']) && ➝ ($_GET['id'] > 0) ) { This conditional is like one from Chapter 12, with the addition of checking that the ID value is greater than 0. Adding that clause doesn’t do anything for the security of the script—the is_numeric() test confirms that the value is safe to use in a query, but prevents the query from being executed if the ID has an unusable value. 5. Define and execute the query: $query = "SELECT quote, source, ➝ favorite FROM quotes WHERE ➝ id={$_GET['id']}"; if ($result = mysqli_query($dbc, ➝ $query)) { The query returns three columns for a specific record. continues on page 415 Script 13.9 continued 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 // Define the query. $query = "SELECT quote, source, favorite FROM quotes WHERE id={$_GET['id']}"; if ($result = mysqli_query($dbc, $query)) { // Run the query. $row = mysqli_fetch_array($result); // Retrieve the information. // Make the form: print '

Quote ' . htmlentities($row['quote']) . '

Source

Is this a favorite?

'; code continues on next page Putting It All Together 413 Script 13.9 continued 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 414 } else { // Couldn't get the information. print '
Could not retrieve the quotation because:
' . mysqli_ error($dbc) . '.
The query being run was: ' . $query . '
'; } } elseif (isset($_POST['id']) && is_numeric($_POST['id']) && ($_POST['id'] > 0)) { // Handle the form. // Validate and secure the form data: $problem = FALSE; if ( !empty($_POST['quote']) && !empty($_POST['source']) ) { // Prepare the values for storing: $quote = mysqli_real_escape_string($dbc, trim(strip_tags($_POST['quote']))); $source = mysqli_real_escape_string($dbc, trim(strip_tags($_POST['source']))); // Create the "favorite" value: if (isset($_POST['favorite'])) { $favorite = 1; } else { $favorite = 0; } } else { print '
Please submit both a quotation and a source.
'; $problem = TRUE; } if (!$problem) { // Define the query. $query = "UPDATE quotes SET quote='$quote', source='$source', favorite=$favorite WHERE id={$_POST['id']}"; if ($result = mysqli_query($dbc, $query)) { print '
The quotation has been updated.
'; } else { print '
Could not update the quotation because:
' . mysqli_ error($dbc) . '.
The query being run was: ' . $query . '
'; } } // No problem! } else { // No ID set. print '
This page has been accessed in error.
'; } // End of main IF. mysqli_close($dbc); // Close the connection. include('templates/footer.html'); // Include the footer. ?> Chapter 13 6. Begin creating the form: print '

Quote ➝ ' . ➝ htmlentities($row['quote']) . ➝ '

Source

Is this a favorite? ➝

'; The print statement starts by closing the checkbox. Then the form must also store the ID value in a hidden input, so that it’s available to the script upon the form submission. Note that it’s safe to print out $_GET['id'] here without using htmlentities() because the is_numeric() function already confirmed that it has a numeric value. reate an error if the record could not 9. C be retrieved: } else { // Couldn't get the ➝ information. print '
Could ➝ not retrieve the quotation ➝ because:
' . mysqli_error ➝ ($dbc) . '.
The query ➝ being run was: ' . $query . ➝ '
'; } 10. Check for a form submission: } elseif (isset($_POST['id']) && ➝ is_numeric($_POST['id']) && ➝ ($_POST['id'] > 0)) { This conditional begins the second phase of the script: handling the submission of the form. The validation is the same as in Step 4, but now $_POST['id'] is referenced instead of $_GET['id']. 416 Chapter 13 11. Validate the form data: $problem = FALSE; if (!empty($_POST['quote']) && ➝ !empty($_POST['source']) ) { The form validation for the edit page mirrors that in the add_quote.php script (Script 13.7). 12. Prepare the values for use in the query: $quote = mysqli_real_escape_string ➝ ($dbc, trim(strip_tags($_POST ➝ ['quote']))); $source = mysqli_real_escape_string ➝ ($dbc, trim(strip_tags($_POST ➝ ['source']))); if (isset($_POST['favorite'])) { $favorite = 1; } else { $favorite = 0; } This code is also taken straight from add_quote.php. 13. Indicate a problem if the form wasn’t completed: } else { print '
➝ Please submit both a ➝ quotation and a source.
'; $problem = TRUE; } 14. If no problem occurred, update the database: if (!$problem) { $query = "UPDATE quotes ➝ SET quote='$quote', ➝ source=$source', ➝ favorite=$favorite WHERE ➝ id={$_POST['id']}"; if ($r = mysqli_query($dbc, ➝ $query)) { print '
The quotation has ➝ been updated.
'; The UPDATE query updates the values of three of the record’s columns. The two string values are enclosed in single quotation marks (within the query); the numeric $favorite value is not. C The result upon successfully editing a record. The WHERE clause, which dictates the record to be updated, is the critical piece. Finally, a simple message indicates the success of the operation C. 15. Indicate a problem if the query failed: } else { print '
➝ Could not update the ➝ quotation because:
' . ➝ mysqli_error($dbc) . '. ➝
The query being run ➝ was: ' . $query . '
'; } 16. C omplete the conditionals: } // No problem! } else { // No ID set. print '
➝ This page has been accessed ➝ in error.
'; } // End of main IF. The else clause applies if no valid ID value is received by the page via either GET or POST. lose the database connection, and 17. C complete the page: mysqli_close($dbc); include('templates/footer.html'); ?> 18. S ave the file, and test in your browser (by clicking a link on view_quotes.php). Putting It All Together 417 Deleting Quotes The script for deleting existing quotations mimics delete_entry.php from Chapter 12. Upon first arriving, assuming that a valid record ID was passed along in the URL, the quote to be deleted is displayed A. If the administrator clicks the submit button, the form will be submitted back to this same page, at which point the record will be removed from the database B. A The first step for deleting a record is confirming the record to be removed. To create delete_quote.php: 1. B egin a new PHP document in your text editor or IDE, to be named delete_quote.php (Script 13.10): Delete a Quotation ➝ '; B Upon submission of the form, the quotation is deleted and a message is printed. Script 13.10 The delete_quote.php script provides the administrator with a way to delete an existing record. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Delete a Quotation'; // Restrict access to administrators only: if (!is_administrator()) { print '
Access Denied!
You do not have permission to access this page.
'; include('templates/footer.html'); exit(); } code continues on next page 418 Chapter 13 2. T erminate the script if the user isn’t an administrator: if (!is_administrator()) { print '
Access Denied! ➝

You do ➝ not have permission to access ➝ this page.
'; include('templates/ ➝ footer.html'); exit(); } continues on next page Script 13.10 continued 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 // Need the database connection: include('../mysqli_connect.php'); if (isset($_GET['id']) && is_numeric($_GET['id']) && ($_GET['id'] > 0) ) { // Display the quote in a form: // Define the query: $query = "SELECT quote, source, favorite FROM quotes WHERE id={$_GET['id']}"; if ($result = mysqli_query($dbc, $query)) { // Run the query. $row = mysqli_fetch_array($result); // Retrieve the information. // Make the form: print '

Are you sure you want to delete this quote?

' . $row['quote'] . '
- ' . $row['source']; // Is this a favorite? if ($row['favorite'] == 1) { print ' Favorite!'; } print '

'; } else { // Couldn't get the information. print '
Could not retrieve the quote because:
' . mysqli_error($dbc) . '.
The query being run was: ' . $query . '
'; } } elseif (isset($_POST['id']) && is_numeric($_POST['id']) && ($_POST['id'] > 0) ) { // Handle the form. 47 code continues on next page Putting It All Together 419 3. Include the database connection: include('../mysqli_connect.php'); 4. V alidate that a numeric ID value was received in the URL: if (isset($_GET['id']) && ➝ is_numeric($_GET['id']) && ➝ ($_GET['id'] > 0) ) { This is the same conditional used in edit_quote.php. 5. Retrieve the record to be deleted: $query = "SELECT quote, source, ➝ favorite FROM quotes WHERE ➝ id={$_GET['id']}"; if ($r = mysqli_query($dbc, ➝ $query)) {$row = ➝ mysqli_fetch_array($r); The standard three fields are retrieved from the database for the record. Because only one record is being addressed in this script, the mysqli_fetch_array() function is called once, outside of any loop. 6. Begin creating the form: print '

Are you sure you want to ➝ delete this quote?

' . $row ➝ ['quote'] . '
- ' . ➝ $row['source']; The form, for the most part, just displays the quotation. 7. Indicate if the quotation is a favorite: if ($row['favorite'] == 1) { print ' Favorite! ➝ '; } This code is the same as that on the view_quotes.php page, indicating that the quote is, in fact, a favorite. Script 13.10 continued 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 420 // Define the query: $query = "DELETE FROM quotes WHERE id={$_POST['id']} LIMIT 1"; $result = mysqli_query($dbc, $query); // Execute the query. // Report on the result: if (mysqli_affected_rows($dbc) == 1) { print '
The quote entry has been deleted.
'; } else { print '
Could not delete the blog entry because:
' . mysqli_ error($dbc) . '.
The query being run was: ' . $query . '
'; } } else { // No ID received. print '
This page has been accessed in error.
'; } // End of main IF. mysqli_close($dbc); // Close the connection. include('templates/footer.html'); ?> Chapter 13 8. Complete the form: print '

'; The form must contain a hidden input that will pass the quote ID back to the page upon form submission. 9. C omplete the mysqli_query() conditional: } else { // Couldn't get the ➝ information. print '
➝ Could not retrieve the quote because:
' . ➝ mysqli_error($dbc) . '. ➝
The query being run ➝ was: ' . $query . '
'; } If the query failed, the MySQL error and the query itself are displayed for debugging purposes. 10. Check for a form submission: } elseif (isset($_POST['id']) && ➝ is_numeric($_POST['id']) && ➝ ($_POST['id'] > 0) ) { This conditional begins the second phase of the script: handling the submission of the form. The validation is the same as in Step 4, but now $_POST['id'] is referenced instead of $_GET['id']. 11. Delete the record: $query = "DELETE FROM quotes ➝ WHERE id={$_POST['id']} LIMIT ➝ 1"; $r = mysqli_query($dbc, $query); The DELETE query will remove the record. The WHERE conditional indicates which specific record is to be removed, and the LIMIT 1 clause is applied as an extra precaution. 12. Report on the result: if (mysqli_affected_rows($dbc) ➝ == 1) { print '
The quote entry has ➝ been deleted.
'; } else { print '
➝ Could not delete the blog ➝ entry because:
' . ➝ mysqli_error($dbc) . '. ➝
The query being run ➝ was: ' . $query . '
'; } If the query succeeded, then one record will have been affected and a message is displayed to the user B. 13. Complete the conditionals: } else { // No ID received. print '
➝ This page has been accessed ➝ in error.
'; } // End of main IF. The else clause applies if no valid ID value is received by the page via either GET or POST. lose the database connection, and 14. C complete the page: mysqli_close($dbc); include('templates/footer.html'); ?> 15. S ave the file, and test in your browser (by clicking a link on view_quotes.php). Putting It All Together 421 Creating the Home Page Last, but certainly not least, there’s the home page. For this site, the home page will be the only page used by the public at large. The home page will show a single quotation, but the specific quotation can be one of the following: n The most recent (the default) n A random quotation n A random favorite quotation To achieve this effect, links will pass different values in the URL back to this same page A. The script should also display administrative links—edit and delete—for the currently displayed quote, if the user is an administrator B. A Values passed in the URL trigger the execution of different queries. B When an administrator views the home page, extra links are displayed. Script 13.11 The home page of the site shows a single quotation at a time, plus administrative links (when appropriate). 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
{$row['quote']}
- {$row['source']}"; // Is this a favorite? if ($row['favorite'] == 1) { print ' Favorite!'; } // Complete the DIV: print '

'; // If the admin is logged in, display admin links for this record: if (is_administrator()) { print "
Quote Admin: Edit <-> Delete
\n"; } code continues on next page Putting It All Together 423 To select a random row in MySQL, use the ORDER BY RAND() clause. This code uses MySQL’s RAND() function, short for random, to return the records in a random order. So this query first selects every record in random order, and then returns only the first in that set. efine the query that selects a random 5. D favorite record: } elseif (isset ➝ ($_GET['favorite'])) { $query = 'SELECT id, quote, ➝ source, favorite FROM quotes ➝ WHERE favorite=1 ORDER BY ➝ RAND() DESC LIMIT 1'; This query is similar to that in Step 4, but it uses a WHERE clause to restrict the pool of possible quotations to just those whose favorite value equals 1. 6. Define the default query: } else { $query = 'SELECT id, quote, ➝ source, favorite FROM quotes ➝ ORDER BY date_entered DESC ➝ LIMIT 1'; } If no value was passed in the URL, then the home page should display the most recently added quotation. To do that, the query orders all the quotes in descending order of date entered and then limits the results to just a single record. xecute the query, and fetch the 7. E returned record: if ($r = mysqli_query($dbc, ➝ $query)) { $row = mysqli_fetch_array($r); 8. Print the quotation: print "
➝ {$row ['quote']}
➝ {$row['source']} "; This code is similar to that in view_quotes.php, but needs to be used only once. 9. Indicate if the quotation is a favorite, and complete the DIV: if ($row['favorite'] == 1) { print ' Favorite! ➝ '; } print '
'; The conditional is the same as in delete_quote.php and view_quotes.php. Script 13.11 continued 47 48 49 50 51 52 53 54 55 56 424 } else { // Query didn't run. print '
Could not retrieve the data because:
' . mysqli_error($dbc) . '.
The query being run was: ' . $query . '
'; } // End of query IF. mysqli_close($dbc); // Close the connection. print '
Latest <-> Random <-> Favorite
'; include('templates/footer.html'); // Include the footer. ?> Chapter 13 10. If the user is an administrator, create links to edit or delete this record: if (is_administrator()) { print "
Quote Admin: ➝ Edit ➝ - + | + Delete
\n"; } If the user is an administrator, links to the edit and delete scripts will be added to the page. The links themselves have values just like those in view_quotes.php. 11. If the query didn’t run, print out an error message: } else { // Query didn't run. print '
➝ Could not retrieve the data because:
' . ➝ mysqli_error($dbc) . '. ➝
The query being run ➝ was: ' . $query . '
'; } // End of query IF. This code is for your own debugging purposes. You would not display a MySQL error, or the query that caused it, to the general public. 13. Create links to other pages: print '
➝ Latest <-> ➝ Random <-> ➝ Favorite
'; Three public links are added to the page, each back to this same script. The first link, which passes no values in the URL, will always show the most recent quotation. The second, which passes a random value in the URL, will trigger the query in Step 4, thereby retrieving a random record. The third link, which passes a favorite value in the URL, will trigger the query in Step 5, thereby retrieving a random favorite record. 14. Include the footer, and complete the page: include('templates/footer.html'); ?> 15. S ave the file, and test in your browser C. Normally the home page is one of the first scripts written, not the last. But in this case I wanted to build up to this point in the example. As a precaution, you could only show the MySQL error if is_administrator() returns TRUE. lose the database connection: 12. C mysqli_close($dbc); The database connection will no longer be needed, so it can be closed at this point. C The latest quotation (note the URL). Putting It All Together 425 Review and Pursue If you have any problems with the review questions or the pursue prompts, turn to the book’s supporting forum (www.LarryUllman.com/forums/). Pursue n n Review n n n n How would the is_administrator() function be called to check for the same cookie—named Samuel—with a different value? A different cookie—not named Samuel—with a different value? hy is the reference to the style sheet in W the header file css/style.css instead of ../css/style.css? How else could the style sheet be referenced? n n n n Why is the login.php script structured the way it is? How could that script be organized more linearly? hat would be some other good ideas W for user-defined functions with this site? Hint: Look for repeated code. n n 426 Chapter 13 Make the login form sticky. efine the login credentials—the cookie D name and value—as constants in a configuration file. Then include that configuration file on every page, and use those constants for creating, deleting, and confirming the value of the cookie. L imit the cookie’s expiration to only 15 minutes, and then re-send the cookie on each page, if appropriate (i.e., if the cookie exists). Use sessions instead of a cookie. Make the add_quote.php and edit_quote.php forms sticky. Change view_quotes.php so that the administrator can list the quotes in different order. Hint: Create links back to the page like those on index.php, and change the query accordingly. efore putting this site on a live server B (should you do that), update all the code so that no MySQL error is ever shown to a nonadministrative user. ee what other repetitive code could S also be moved into your own functions. A Installation and Configuration The three technical requirements for executing all of this book’s examples are PHP, the scripting language; the web server application that PHP runs through; and MySQL, the database application. This appendix describes the installation of these tools on two different platforms—Windows 10 and Mac OS X. If you are using a hosted website, all of this will already be provided for you, but these products are all free and easy enough to install, so putting them on your own computer still makes sense. After the installation section, this appendix demonstrates some basics for working with MySQL and configuring PHP. The PHP and MySQL manuals cover installation and configuration in a reasonable amount of detail. You may want to also peruse them, particularly if you encounter problems. Installation on Windows Although you can certainly install a web server (such as Apache, Nginx, or IIS), PHP, and MySQL individually on a Windows computer, I strongly recommend you use an all-in-one installer instead. It’s simply easier and more reliable to do so. Several all-in-one installers are out there for Windows. The four that I see mentioned most frequently are n XAMPP (www.apachefriends.org) n WAMP (www.wampserver.com) n AMPPS (www.ampps.com) n itnami (www.bitnami.com), which also B partners with XAMPP For this appendix, I’ll use XAMPP, which runs on Windows 2008, 2012, Vista, 7, and 8. (The XAMPP site makes no mention of Windows 10, but you should be able to use XAMPP on that version of Windows too.) 428 Appendix A On Firewalls A firewall prevents communications in many ways, the most common of which being over ports: an access point to a computer. Versions of Windows starting with Service Pack 2 of XP include a built-in firewall. You can also download and install third-party firewalls. Firewalls improve the security of your computer, but they may also interfere with your ability to run Apache, MySQL, and some of the other tools used by XAMPP because they all use ports. When running XAMPP for the first time, or during the installation process, if you see a security prompt indicating that the firewall is blocking Apache, MySQL, or the like, choose Unblock or Allow access. Otherwise, you can configure your firewall manually through the operating system settings. The ports that need to be open are as follows: 80 for Apache, 3306 for MySQL, and 25 for the Mercury mail server. If you have any problems starting or accessing one of these, disable your firewall and see if it works then. If so, you’ll know the firewall is the problem and that it needs to be reconfigured. Just to be clear, firewalls aren’t found just on Windows, but in terms of the instructions in this appendix, the presence of a firewall will more likely trip up a Windows user than any other. Along with Apache, PHP, and MySQL, XAMPP also installs the following: n hpMyAdmin, the web-based interface p to a MySQL server n OpenSSL, for secure connections n A mail server (for sending email) n Several useful extensions As of this writing, XAMPP (Version 7.0.6) installs PHP 7.0.6, Apache 2.4.18, and phpMyAdmin 4.5.1. There is one catch, however! As of XAMPP 5.5.30, the installer includes MariaDB (www.mariadb.com) instead of MySQL. MariaDB is an open source fork of MySQL that is functionally equivalent. Despite the fact that XAMPP installs MariaDB instead of MySQL, you shouldn’t have any problems following all the MySQLspecific instructions or code in this book. I’ll run through the installation process in these next steps. Note that if you have any problems, you can use the book’s supporting forum (www.LarryUllman.com/forums/), but you’ll probably have more luck turning to the XAMPP site (it is their product, after all). Also, the installer works really well and isn’t that hard to use, so rather than detail every single step in the process, I’ll highlight the most important considerations. Installation and Configuration 429 To install XAMPP on Windows: 1. D ownload the latest release of XAMPP for Windows from www.apachefriends.org A. I suggest that you grab the latest version of PHP available, although you’ll be fine with this book’s content if you use a PHP 5 version instead. n your computer, double-click the 2. O downloaded file to begin the installation process. 3. When prompted B, install all the components. A From the Apache Friends website, grab the latest installer for Windows. Admittedly, you don’t need Tomcat— a Java server—or Perl, but it’s fine to install them too. 4. W hen prompted C, install XAMPP somewhere other than in the Program Files directory. You shouldn’t install it in the Program Files directory because of a permissions issue in Windows. I recommend installing XAMPP in your root directory (e.g., C:\). Wherever you decide to install the program, make note of that location, because you’ll need to know it several other times as you work through this appendix. B The XAMPP components that can be installed. C Select where XAMPP should be installed. 430 Appendix A 5. A fter the installation process has done its thing D, opt to start the XAMPP Control Panel. o start, stop, and configure XAMPP, 6. T use the XAMPP Control Panel E. D The installation of XAMPP is complete! Apache has to be running for every chapter in this book. MySQL must be running for Chapter 12, “Intro to Databases,” and Chapter 13, “Putting It All Together.” Mercury is the mail server that XAMPP installs. It needs to be running in order to send email using PHP (see Chapter 8, “Creating Web Applications”). 7. Immediately set a password for the root MySQL user. How you do this is explained in the “Managing MySQL Users” section later in this appendix. continues on next page E The XAMPP Control Panel, used to manage the software. Installation and Configuration 431 The XAMPP Control Panel’s various admin links will take you to different web pages (on your server) and other resources F. See the “Configuring PHP” section to learn how to configure PHP by editing the php.ini file. Whenever you restart your computer, you’ll need to restart the XAMPP services. Your web root directory—where your PHP scripts should be placed in order to test them— is the htdocs folder in the directory where XAMPP was installed. Following my installation instructions, this would be C:\xampp\htdocs. 432 Appendix A F The web-based splash page for XAMPP, linked from its Control Panel. Installation on Mac OS X Mac OS X is at its heart a version of Unix, and because PHP and MySQL were originally written for Unix-like systems, numerous options are available for installing them on Mac OS X. In fact, Mac OS X already comes with Apache installed, saving you that step. Seasoned developers and those at home in the Terminal will likely want to install PHP and MySQL using package installers such as http://php-osx.liip.ch/ and Homebrew (http://brew.sh/). But for beginners, I recommend using an all-in-one installer such as n XAMPP (www.apachefriends.org) n AMPPS (www.ampps.com) n n itnami (www.bitnami.com), which also B partners with XAMPP MAMP (www.mamp.info) Not only are these installers relatively foolproof, but they also won’t leave you scrambling when an operating system update overwrites your Apache configuration file. For this appendix, I’ll use XAMPP, which runs on Mac OS X 10.6 and later. Along with Apache, PHP, and MySQL, XAMPP also installs the following: n hpMyAdmin, the web-based interface p to a MySQL server n OpenSSL, for secure connections n Several useful extensions As of this writing, XAMPP (Version 7.0.6) installs PHP 7.0.6, Apache 2.4.18, and phpMyAdmin 4.5.1. There is one catch, however! As of XAMPP 5.5.30, the installer includes MariaDB (www.mariadb.com) instead of MySQL. MariaDB is an open source fork of MySQL that is functionally equivalent. Despite the fact that XAMPP installs MariaDB instead of MySQL, you shouldn’t have any problems following all the MySQLspecific instructions or code in this book. I’ll run through the installation process in these next steps. Note that if you have any problems, you can use the book’s supporting forum (www.LarryUllman.com/forums/), but you’ll probably have more luck turning to the XAMPP site (it is their product, after all). Also, the installer works really well and isn’t that hard to use, so rather than detail every single step in the process, I’ll highlight the most important considerations. Installation and Configuration 433 To install XAMPP on Mac OS X: 1. D ownload the latest release of XAMPP for Mac OS X from www.apachefriends.org A. I suggest you grab the latest version of PHP available, although you’ll be fine with this book’s content if you use a PHP 5 version instead. n your computer, double-click the 2. O downloaded file to mount the disc image. A From the Apache Friends website, grab the latest installer for Mac OS X. 3. In the mounted disk image, doubleclick the package installer to begin the installation process. 4. When prompted B, install all the components. You’ll see only two, broad options; install both. 5. A fter the installation process has done its thing C, opt to launch XAMPP. 6. T o start, stop, and configure XAMPP, use the XAMPP Control Panel D. Apache has to be running for every chapter in this book. MySQL must be running for Chapters 12 and 13. You probably won’t ever need the FTP application, because you can just move your files directly. B The XAMPP components that can be installed. 7. Immediately set a password for the root MySQL user. How you do this is explained in the “Managing MySQL Users” section later in this appendix. C The installation of XAMPP is complete! 434 Appendix A See the “Configuring PHP” section to learn how to configure PHP by editing the php.ini file. Whenever you restart your computer, you’ll need to restart the XAMPP services. Your web root directory—where your PHP scripts should be placed in order to test them—is the htdocs folder in the directory where XAMPP was installed. This would be /Applications/XAMPP/xamppfiles/ htdocs. D The XAMPP Control Panel, used to manage the software. Installation and Configuration 435 Configuring PHP 2. In the browser’s output, search for Loaded Configuration File. One of the benefits of installing PHP on your own computer is that you can configure it however you prefer. How PHP runs is determined by the php.ini file, which is normally created when PHP is installed. The value next to this text is the location of the active configuration file. This will be something like C:\xampp\php\ php.ini or /Applications/XAMPP/ xamppfiles/etc/php.ini. Two of the most important settings you may want to consider adjusting are display_errors and error_reporting (both are discussed in Chapter 3, “HTML Forms and PHP”). To change any setting, open the PHP configuration file, edit it as needed, then save it and restart the web server. If there is no value for the Loaded Configuration File, your server has no active php.ini file. This is highly uncommon, but you’d need to download the PHP source code, from www.php.net, to find a sample configuration file. 3. Open the php.ini file in any text editor. 4. Change the settings as you wish. To alter PHP’s configuration: Depending on your operating system, you may need to be an administrator or enter a password to make changes to this file. 1. In your browser, execute a script that invokes the phpinfo() function A. The phpinfo() function, discussed in Chapter 1, “Getting Started with PHP,” reveals oodles of information about the PHP installation. Many instructions are included in the file. Lines are commented out (made inactive) by preceding them with a semicolon. 5. Save the php.ini file. A Some of the output from calling the phpinfo() function. 436 Appendix A Enabling Mail The mail() function works only if the computer running PHP has access to sendmail or another mail server. One way to enable the mail() function is to set the smtp value in the php.ini file (for Windows only). This approach works if, for example, your Internet provider has an SMTP address you can use. Unfortunately, you can’t use this value if your ISP’s SMTP server requires authentication. For Windows, a number of free SMTP servers, such as Mercury, are available. It’s installed along with XAMPP, or you can install it yourself if you’re not using XAMPP. 6. Restart your web server. You don’t need to restart the entire computer, just the web server (e.g., Apache). In XAMPP, simply click Stop and then Start for Apache. You can also use the phpinfo() function to confirm that your configuration changes have taken effect. If you edit the php.ini file and restart the web server but your changes don’t take effect, make sure you’re editing the proper php.ini file (you may have more than one on your computer). Mac OS X comes with a mail server installed—postfix and/or sendmail—that needs to be enabled. Search Google for instructions on manually enabling your mail server on Mac OS X. Alternatively, you can search some of the PHP code libraries to learn how to use an SMTP server that requires authentication. Installation and Configuration 437 MySQL Interfaces In Chapters 12 and 13, a PHP script will be used to interact with a MySQL database. As I explain in Chapter 12, being able to interact with MySQL independent of your PHP scripts is the most valuable debugging tool there is. Knowing how to use a separate MySQL interface is therefore critical information. I’ll quickly introduce the two most common options. Using the MySQL client The MySQL software comes with an important tool known as the MySQL client. This application provides a simple interface for communicating with the MySQL server. It’s a command-line tool that must be accessed using the Terminal application on Linux and Mac OS X or through the command (DOS) prompt on Windows. To use the MySQL client: 1. Make sure the MySQL server is running. If you’re using XAMPP on Windows, you can start MySQL there and then skip ahead to Step 3. 2. Find the MySQL bin directory. To connect to the client, you’ll need to know where it’s located. The MySQL client is found within the bin directory for your installation (bin is short for “binary,” which is to say an executable). I’ll run through the common possibilities. If you installed MySQL yourself, the client’s location depends on where you installed the software, but it’s most likely C:\mysql\bin\mysql (Windows) or /usr/local/mysql/bin/mysql (Mac OS X and Unix) 438 Appendix A Using Semicolons Within the MySQL client, a semicolon indicates the completion of a statement to be executed. This allows you to write a complicated command or SQL query over multiply lines, and MySQL won’t attempt to run that command until it meets a semicolon. This is only a requirement within the MySQL client, though. Queries run through PHP scripts or phpMyAdmin do not need to be terminated by semicolons. And you don’t need to use a semicolon after exit to leave the MySQL client. If you used XAMPP on Windows, it’s C:\xampp\mysql\bin\mysql (assuming you installed XAMPP in C:\). If you installed XAMPP on Mac OS X, it’s /Applications/XAMPP/xamppfiles/bin. 3. Access a command prompt. A Use the Run dialog to access a console window on Windows. On Mac OS X and Unix, you can accomplish this by running the Terminal application. On Mac OS X, it’s found within the /Applications/Utilities folder. On Windows, press Command+R to open the Run dialog, and at the prompt, type cmd and press Enter or click OK A. If you’re using XAMPP on Windows, click the Shell button in the Control Panel B to access a command prompt. 4. Attempt to connect to the MySQL server. B The Shell button in the XAMPP Control Panel takes you straight to a command prompt. To connect, enter the pathname identified in Step 2 plus -u username -p. So, the command might be C:\mysql\bin\mysql -u username -p (Windows) or /usr/local/mysql/bin/mysql ➝ -u username -p (Unix and Mac OS X) or /Applications/XAMPP/xamppfiles/ ➝ bin/mysql -u username -p (Mac OS X) For XAMPP on Windows, you can just use mysql -u username -p (assuming you clicked the Shell button in Step 3). Replace username with the username you want to use. If you haven’t yet created any other users, this will be root (root is the supreme MySQL user). If you haven’t yet established a root user password (the default behavior for XAMPP), you can omit the -p flag. continues on next page Installation and Configuration 439 5. Enter the password at the prompt C. The password requested is the MySQL password for the user named during the connection. You’ll see this prompt only if you used the -p option in Step 4. If you installed MAMP on Mac OS X, the password for the root user will be root. If you installed XAMPP on Windows, no password is set initially. 6. List the available databases D: 7. Exit the MySQL client. To do so, type exit or quit. If you see a Can’t connect to local MySQL server through socket… error message, it normally means MySQL isn’t running. The MySQL client is one of the best tools for debugging PHP scripts that work with MySQL. You can use the MySQL client to check user permissions and to run queries outside of the PHP script. SHOW DATABASES; The SHOW DATABASES command is a SQL query that lists every database hosted on that MySQL installation that the connected user can see. C Successfully accessing the MySQL client on Windows. D After a fresh MySQL installation, there will only be a couple of databases. 440 Appendix A Using phpMyAdmin To use phpMyAdmin: phpMyAdmin (www.phpmyadmin.net) is a web-based interface for interacting with a MySQL server, allowing you to create tables, import and export records, and much more, without having to use a commandline interface. It is arguably the most popular web software written in PHP, as every PHP hosting company provides it. In fact, the all-in-one XAMPP installer includes it too. phpMyAdmin is well documented and easy to use, but I’ll highlight a couple of quick points. 1. A ccess phpMyAdmin in your browser E. When using XAMPP, phpMyAdmin is available at http://localhost/phpmyadmin/. On Windows, you can also get to this page by clicking the MySQL admin link in the Control Panel. 2. C lick a database name in the left column to select that database. continues on next page E The phpMyAdmin front page. Installation and Configuration 441 3. C lick a table name in the left column to select that table F. You don’t always have to select a table, but by doing so you can simplify some tasks. 4. U se the tabs and links (on the right side of the page) to perform common tasks. For the most part, the tabs and links are shortcuts to common SQL commands. For example, the Browse tab performs a SELECT query and the Insert tab creates a form for adding new records. 5. U se the SQL tab to execute any SQL command. You can alternatively use the SQL Query Window, linked just above the list of database or table names. Using either interface, you can test queries that your PHP scripts are using, without the added complication of the script itself. Many other clients are available for interacting with a MySQL database, but the MySQL command-line client and phpMyAdmin are the two most common. F Selecting a database or a table, from the left column, changes the options on the right side of the page. 442 Appendix A Managing MySQL Users Once you’ve successfully installed MySQL, you can begin creating MySQL users. A MySQL user is a fundamental security concept, limiting access to, and influence over, stored data. Just to clarify, your databases can have several different users, just as your operating system might. But MySQL users are different from operating system users. While learning PHP and MySQL on your own computer, you don’t necessarily need to create new users, but live production sites need to have dedicated MySQL users with appropriate permissions. The initial MySQL installation comes with one user (named root) with no password set. At the very least, you should create a new, secure password for the root user after installing MySQL. After that, you can create other users with more limited permissions. As a rule, you shouldn’t use the root user for normal, day-to-day operations. While you’re creating new users, you’ll also see how to create new databases, which will be necessary for Chapters 12 and 13. Setting the root user password You can set any user’s password using either phpMyAdmin or the MySQL client, as long as the MySQL server is running. If MySQL isn’t currently running, start it now using the steps outlined earlier in this appendix. You must be connected to MySQL as the root user in order to be able to change the root user’s password. To assign a password to the root user via the MySQL client: 1. C onnect to the MySQL client. See the set of steps in “To use the MySQL client” for detailed instructions. nter the following command, replacing 2. E thepassword with the password you want to use A: SET PASSWORD FOR ➝ 'root'@'localhost' = ➝ PASSWORD('thepassword'); Keep in mind that passwords in MySQL are case-sensitive, so Kazan and kazan aren’t interchangeable. The term PASSWORD that precedes the actual quoted password tells MySQL to encrypt that string using the MySQL PASSWORD() function. You cannot have a space between PASSWORD and the opening parenthesis. When you install MySQL, no value—or no secure password—is established for the root user. This is certainly a security risk that should be remedied before you begin to use the server (because the root user has unlimited powers). continues on next page A Updating the root user’s password using SQL within the MySQL client. Installation and Configuration 443 3. Exit the MySQL client: exit 4. T est the new password by logging in to the MySQL client again. Now that a password has been established, you need to add the -p flag to the connection command. You’ll see an Enter password prompt, where you enter the just-created password. B The list of MySQL users, as shown in phpMyAdmin. To assign a password to the root user via phpMyAdmin: 1. Open phpMyAdmin in your browser. See the set of steps in the section “To use phpMyAdmin” for detailed instructions. n the home page, click the User 2. O accounts tab. You can always click the home icon, in the upper-left corner, to get to the phpMyAdmin home page. 3. In the list of users, click the Edit Privileges icon on the root user’s row B. 4. O n the next page, click Change Password. 5. U se the Change Password form C, found further down the resulting page, to change the password. 444 Appendix A C The form for updating a MySQL user’s password within phpMyAdmin. 6. C hange the root user’s password in phpMyAdmin’s configuration file, if necessary. The result of changing the root user’s password will likely be that phpMyAdmin is denied access to the MySQL server. This is because phpMyAdmin, on a local server, normally connects to MySQL as the root user, with the root user’s password hard-coded into a configuration file. After following Steps 1–4, find the config.inc.php file in the phpMyAdmin directory—likely /Applications/XAMPP/ xamppfiles/phpmyadmin (Mac OS X with XAMPP) or C:\xampp\phpMyAdmin (Windows with XAMPP). Open that file in any text editor or IDE and change this next line to use the new password: $cfg['Servers'][$i]['password'] = ➝ 'thepassword'; Then save the file, and reload phpMyAdmin in your browser. Creating a database, users, and privileges After you have MySQL successfully up and running, and after you’ve established a password for the root user, you can add other users. This is commonly done as part of creating new databases: To improve the security of your databases, you should always create new users to access your databases rather than using the root user at all times. To create a database, simply run a CREATE DATABASE command: CREATE DATABASE database_name The database name can contain numbers, letters, a dollar sign, and an underscore, but not spaces. You can run this command only if you are connected as a user with CREATE DATABASE permissions. The MySQL privileges system was designed to ensure proper authority for certain commands on specific databases. This technology is how a web host, for example, can let several users access several databases without concern. Each user in the MySQL system can have specific capabilities on specific databases from specific hosts (computers). The root user— the MySQL root user, not the system’s—has the most power and is used to create subusers, although subusers can be given rootlike powers (inadvisably so). Installation and Configuration 445 When a user attempts to do something with the MySQL server, MySQL first checks to see if the user has permission to connect to the server at all (based on the username, the user’s host, the user’s password, and the information in the mysql database’s user table). Second, MySQL checks to see if the user has permission to run the specific SQL statement on the specific databases—for example, to select data, insert data, or create a new table. Table A.1 lists most of the various privileges you can set on a user-by-user basis. You can set users and privileges in MySQL in a handful of ways, but I’ll start by discussing the GRANT command. The syntax goes like this: GRANT privileges ON database.* ➝ TO 'username'@'hostname' ➝ IDENTIFIED BY 'password' For the privileges aspect of this statement, you can list specific privileges from Table A.1, or you can allow for all of them by using ALL (which isn’t prudent). The database.* part of the statement specifies which database and tables the user can work on. You can name specific tables using the database.tablename syntax or allow for every database with *.* (again, not prudent). Finally, you can specify the username, hostname, and a password. The username has a maximum length of 32 characters (as of MySQL 5.7.8; it was 16 in earlier versions). When you’re creating a username, be sure to avoid spaces—use the underscore instead, and note that usernames are case-sensitive. 446 Appendix A TABLE A.1 MySQL Privileges PRIVILEGE ALLOWS SELECT Read rows from tables. INSERT Add new rows of data to tables. UPDATE Alter existing data in tables. DELETE Remove existing data from tables. INDEX Create and drop indexes in tables. ALTER Modify the structure of a table. CREATE Create new tables or databases. DROP Delete existing tables or databases. RELOAD Reload the grant tables (and therefore enact user changes). SHUTDOWN Stop the MySQL server. PROCESS View and stop existing MySQL processes. FILE Import data into tables from text files. GRANT Create new users. REVOKE Remove users’ permissions. The hostname is the computer from which the user is allowed to connect. This could be a domain name, such as www.example.com, or an IP address. Normally, localhost is specified as the hostname, meaning that the MySQL user must be connecting from the same computer that the MySQL database is running on. To allow for any host, use the hostname wildcard character (%): To create new users using GRANT: 1. L og in to the MySQL client as a root user. Use the steps already explained to do this. You must be logged in as a user capable of creating databases and other users. 2. Create a new database D: GRANT privileges ON database.* TO ➝ 'username'@'%' IDENTIFIED BY ➝ 'password' But that is also not recommended. When it comes to creating users, it’s best to be explicit and confining. CREATE DATABASE myblog; This particular database will be used in Chapter 12. 3. C reate a user with administrative-level privileges on the myblog database E: GRANT SELECT, INSERT, UPDATE, ➝ DELETE, CREATE, DROP, ALTER, ➝ INDEX ON myblog.* TO 'llama'@ ➝ 'localhost' IDENTIFIED BY ➝ 'camel'; The password has no length limit but is also case-sensitive. The passwords are encrypted in the MySQL database, meaning they can’t be recovered in a plain text format. Omitting the IDENTIFIED BY 'password' clause results in that user not being required to enter a password (which, once again, should be avoided). This user, llama, can create tables, alter tables, insert data, update data, and so forth, on the temp database. This essentially includes every administrativelevel capability aside from creating new users. Be certain to use a password— perhaps more clever than the one used here. As an example of this process, you’ll create two new users with specific privileges on a new database named myblog. Keep in mind that you can grant permissions only to users on existing databases. This next sequence will also show how to create a database. continues on next page D Creating a new database. E Creating an administrative-level user for a single database. Installation and Configuration 447 4. C reate a user with basic access to the database F: The changes just made won’t take effect until you’ve told MySQL to reset the list of acceptable users and privileges, which is what this command does. Forgetting this step and then being unable to access the database using the newly created users is a common mistake. GRANT SELECT, INSERT, UPDATE, ➝ DELETE ON myblog.* TO 'webuser'@ ➝ 'localhost' IDENTIFIED BY ➝ 'BroWs1ng'; Now the generic webuser can browse through records (SELECT from tables) as well as add, edit, and delete them, but this user can’t alter the structure of the database. When you’re establishing users and privileges, work your way from the bottom up, allowing the bare minimum of access at all times. Any database whose name begins with test_ can be modified by any user who has permission to connect to MySQL. Therefore, be careful not to create a database named this way unless it truly is experimental. The REVOKE command removes users and permissions. 5. Apply the changes G: FLUSH PRIVILEGES; F This user has more restricted rights to the same database. G Don’t forget this step before you try to access MySQL using the newly created users. 448 Appendix A B Resources and Next Steps This book was written to give beginning PHP programmers a good foundation on which to base their learning. A few topics have been either omitted or glossed over, because the book focuses on covering the absolute fundamentals. This appendix lists a number of useful resources, briefly discusses where to obtain more information for databases and some uncovered topics, and includes a few tables, both old and new. Along with those sites included here, you should check out the book’s companion website at www.LarryUllman.com. There you’ll find all of the book’s code, a support forum, an errata page, and more. The PHP Manual All PHP programmers should familiarize themselves with, and possibly acquire, some version of the PHP manual before beginning to work with the language. The manual is available from the official PHP site—www.php.net/docs.php—as well as from a number of other locations. You can download the manual in nearly a dozen languages in different formats. The official website also has an annotated version of the manual available at www.php.net/manual/en/ (in English), where users have added helpful notes and comments. If you’re having problems with a particular function, reading the manual’s page for that function will likely provide an answer. A trick pointed out in Chapter 1, “Getting Started with PHP,” is that you can quickly access the documentation page for any specific function by going to www.php.net/functionname. For example, the page for the number_format() function is www.php.net/number_format. Database Resources Which database resources will be most useful to you depends, obviously, on which database management system (DBMS) you’re using. The most common database used with PHP is probably MySQL, but PHP supports all the standard database applications. To learn more about using MySQL, begin with the official MySQL website (www.mysql.com). You can download the MySQL manual to use as a reference while you work. If you’re using MySQL, don’t forget to download and install phpMyAdmin (www.phpmyadmin.net). Written in PHP, this is an invaluable tool for working with a database and much more approachable for beginners than some other interfaces. Another area of database resources you should delve into is SQL. Websites discussing SQL, the language used by every database application, include the following: n n n n SQL Course (www.sqlcourse.com) Gentle Introduction to SQL A (www.sqlzoo.net) 3Schools’ SQL Tutorial W (www.w3schools.com/sql/) SQL.org (www.sql.org) (All of the above are a bit dated in appearance, but the content still applies.) My PHP and MySQL for Dynamic Web Sites: Visual QuickPro Guide (Peachpit Press, 2012) also discusses SQL and MySQL in much greater detail than this book. 450 Appendix B Top 10 Frequently Asked Questions (or Problems) Debugging is a valuable skill that takes time and experience to fully develop. But rather than send you off on that journey ill-equipped, I’ve included the 10 most frequently seen problems in PHP scripts, along with the most likely causes. First, though, here are five of my best pieces of advice when it comes to debugging a problem: n Run all PHP scripts through a URL. Trust the error message! Many beginners have more difficulty than they should in solving a problem because they don’t pay attention to the error message they see. Although some of PHP’s error messages are cryptic and a few can even be misleading, if PHP says there’s a problem on line 22, the problem is probably on line 22. With a parse error, maybe the actual problem was a missing semicolon on line 21. n void “trying” things to fix A a problem! If you’re not sure what’s causing the problem and what the proper fix is, avoid trying random things as a solution. You’ll likely create new issues this way and only further confuse the original problem. now what version of PHP K you’re running. Some problems are specific to a version of PHP. Use the phpinfo() function to test the version in use whenever you use a server for the first time. Also make sure you know what version of MySQL you’re using, if applicable; the operating system; and the web server (e.g., Apache 2.4). n n n Take a break! The best piece of advice I can offer is to step away from the computer and take a break. I’ve solved many, many problems this way. Sometimes a clear head is what you need. If you don’t run a PHP script through a URL—and this includes the submission of a form to a PHP script—the web server will not handle the request, meaning that PHP will never execute the code. Resources and Next Steps 451 Moving on, here are the top 10 likely problems you’ll encounter in PHP: n ndefined variable or undefined index U error A These errors occur when error reporting is set on its highest level, and they may or may not indicate a problem. Check the spelling of each variable or array index to make sure it’s correct. Then make sure you initialize variables prior to referring to them. Also make sure, of course, that variables that should have a value actually do! Variables that don’t have a value Perhaps you referred to a variable by the wrong name. Double-check your capitalization and spelling of variable names, and then be certain to use $_GET, $_POST, $_COOKIE, and $_SESSION as appropriate. If need be, use the print_r() function to see the value of any variable. Blank pages If you see a blank screen in your browser after submitting a form or loading a PHP script, it’s most likely because an error occurred that terminated the execution of the page. First check the HTML source code to see if it’s an HTML problem. Then turn on display_errors in your php.ini configuration file or PHP script to see what PHP problem could be occurring. n n n Call to undefined function… error Such an error message means you’re attempting to use a function that PHP doesn’t have. This problem can be caused by a misspelling of a function name, failure to define your own function before calling it, or using a function that’s not available in your version of PHP. Check your spelling and the PHP manual for a non-user-defined function to find the problem. A Errors complaining about undefined variables or indexes often come from spelling or capitalization mistakes. 452 Appendix B n This error message indicates that you’ve used an HTTP header-related function—header(), setcookie(), or session_start()—after the browser has already received HTML or even a blank space. Double-check what occurs in a script before you call any of these functions. You can also use output buffering to prevent these errors from occurring. n the database using a different interface (such as the MySQL client). Headers already sent error B Access denied error C If you see this message while attempting to work with a database, then the username, password, and host combination you’re using doesn’t have permission to access the database. This isn’t normally a PHP issue. Confirm the values that are being used, and attempt to connect to n upplied argument is not a valid S MySQL result resource error This is another database-related error message. The message means that a query result is being used inappropriately. Most frequently, this is because you’re trying to fetch rows from a query that didn’t return any records, commonly due to badly formed SQL. To solve this problem, print out the query being run, and test it using another tool (such as the MySQL client or phpMyAdmin). Also check that you’ve been consistent with your variable names. continues on next page B Some functions create headers already sent errors if called at the wrong time. C If the MySQL access information is incorrect, you’ll see a message saying that database access has been denied. Resources and Next Steps 453 n Preset HTML form values are cut off You must put the value attribute of an HTML form input within double quotation marks. If you fail to do so, only the part of the value up to the first space will be set as that input’s value. n onditionals or loops behave C unpredictably These logical errors are quite common. Check that you haven’t used the wrong operator (such as = instead of ==) and that you refer to the proper variables. Then use print statements to let you know what the script is doing. n Parse errors D Parse errors are the most ubiquitous problems you’ll deal with. Even the most seasoned PHP programmer sees them occasionally. Check that every statement concludes with a semicolon and that all quotation marks, parentheses, braces, and brackets are evenly paired. If you still can’t find the parse error, comment out large sections of the script using the /* and */ characters. Uncomment a section at a time until you see the parse error again. Then you’ll know where in the script the problem is (or most likely is). 454 Appendix B D Parse errors are all too common and prevent scripts from executing. Next Steps This book will get you started using PHP, but you might want to investigate a few topics further. Before taking on more topics, however, you should get more experience. If you need a good library of problems to work through, check out Project Euler (https://projecteuler.net/archives). Security Web servers, operating systems, databases, and PHP security are all topics that merit their own books. Although this book demonstrates writing secure web applications, there’s always room for you to learn more in this area. Start by checking out these sites: n Study in Scarlett A (www.securereality.com.au/ studyinscarlett/) This is an article about writing secure PHP code. It’s old but still has fundamental concepts. Object-oriented programming The subject of objects and object-oriented programming (OOP) is not covered in this book for two reasons: n n It’s well beyond the scope of a beginner’s guide. ou won’t be restricted as to what Y you can do in PHP by not understanding objects. When you decide you want to learn the subject, you can search the PHP sites for tutorials, check out a framework (see the next section of this appendix), or read my PHP Advanced and Object-Oriented Programming: Visual QuickPro Guide (Peachpit Press, 2013). I dedicate around 150 pages of that book just to OOP (and there are still aspects of OOP that I didn’t get to)! Frameworks he Open Web Application Security T Project (www.owasp.org) A framework is an established library of code that you can use to develop sophisticated web applications. By reusing someone else’s proven code, you can quickly build parts or all of a website. This is a standard resource for web security, and its Top Ten list (www.owasp.org/index.php/ Category:OWASP_Top_Ten_Project) is a must-read. There are many PHP frameworks available, starting with the Zend Framework (http:// framework.zend.com). This framework was created by some of the key people behind PHP and is well documented. You should also read the relevant sections of the PHP manual and the manual for the database you’re using. Searching the Internet for PHP and security will turn up many interesting articles as well. Pay attention to the dates of articles you read, though, so you do not pick up outdated habits! My personal favorite PHP framework, as of this writing, is Yii (www.yiiframework.com). I write about Yii extensively on my site. Many developers are fans of Laravel (https:// laravel.com/), which you ought to consider. n Resources and Next Steps 455 This book’s esteemed technical editor, Paul Reinheimer, is a big fan of microframeworks, such as Slim (www.slimframework.com). Many people love frameworks and what they offer. On the other hand, it does take some time to learn how to use a framework, and customizing the framework’s behavior can be daunting. JavaScript JavaScript is a client-side technology that runs in the browser. It can be used to add various dynamic features to a website, from simple eye candy to interactive menus and forms. Because it runs within the browser, JavaScript provides some functionality that PHP cannot. And, like PHP, JavaScript is relatively easy to learn and use. For more, see n n n JavaScript.com (www.javascript.com) ozilla Developer Network M (https://developer.mozilla.org/en-US/ docs/Web/JavaScript) 3School’s JavaScript pages W (www.w3schools.com/js/) I highly recommend you consider learning jQuery (www.jquery.com) to help you with your JavaScript needs. jQuery is a JavaScript framework that’s easy to use, powerful, and pretty well documented. It’s on the verge of being overly used, but it’s a great and reliable way to get started with JavaScript. Other books It is my hope that after reading this book you’ll be interested in learning more about PHP and web development in general. Although I could recommend books by other writers, there’s an inherent conflict 456 Appendix B there and my opinion as a rival writer would not be the same as yours as a reader. So, instead, I’ll just quickly highlight a couple of my other books and how they compare to this one. PHP and MySQL for Dynamic Web Sites: Visual QuickPro Guide, Fourth Edition (Peachpit Press, 2012) is kind of a companion to this book. There is some overlap in content, particularly in the early chapters, but the examples are different, and it goes at a faster pace. MySQL and SQL in particular get a lot more coverage, and there are three different example chapters: a multilingual forum, a user registration and login system, and an e-commerce setup. My PHP Advanced and Object-Oriented Programming: Visual QuickPro Guide, Third Edition (Peachpit Press, 2013) is kind of a companion to the PHP and MySQL book just mentioned. This book is much more advanced, spending a lot of time on topics such as OOP. It’s not intended to be read as linearly as this one, but rather each chapter focuses on a specific topic. My book Effortless E-Commerce with PHP and MySQL (New Riders, 2014) covers everything you need to know to create fully functioning e-commerce sites. The book uses two specific examples for doing so, and incorporates two different payment systems. Complete comfort with PHP and MySQL is assumed, however. Finally, my Modern JavaScript: Develop and Design (New Riders, 2012) teaches you this very important programming language using today’s modern techniques. There’s even a chapter dedicated to using PHP and JavaScript together! Tables This book has a handful of tables scattered about, the three most important of which are reprinted here as a convenient reference. You’ll also find one new table that lists operator precedence (Table B.1). This partial list goes from highest to lowest (for example, multiplication takes precedence over addition). TABLE B.2 PHP’s Operators Operator Usage Type + Addition Arithmetic - Subtraction Arithmetic * Multiplication Arithmetic / Division Arithmetic % Modulus (remainder of a division) Arithmetic ++ Incrementation Arithmetic -- Decrementation Arithmetic = ssigns a value A to a variable Assignment == Equality Comparison != Inequality Comparison < Less than Comparison > Greater than Comparison <= L ess than or equal to Comparison >= Greater than or equal to Comparison ! Negation Logical AND And Logical && And Logical OR Or Logical || Or Logical XOR Exclusive or Logical <=> Null coalescing Logical + - . . Concatenation String < <= > >= .= Concatenates to the value of a variable Combined concatenation and assignment += dds to the A value of a variable Combined arithmetic and assignment -= Subtracts from the value of a variable Combined arithmetic and assignment Table B.2 lists PHP’s main operators and their types. It’s most important to remember that a single equals sign (=) assigns a value to a variable, whereas two equals signs (= =) are used together to check for equality. TABLE B.1 Operator Precedence ++ -! * / % == != === !== <=> && || = += -= *= /= .= %= and xor or Resources and Next Steps 457 The various formats for the date() function may be one of the hardest things to remember. Keep Table B.3 nearby when you’re using the date() function. TABLE B.3 Date( ) Function Formatting Character Meaning Example Y Year as 4 digits 2017 y Year as 2 digits 17 L Is it a leap year? 1 (for yes) n Month as 1 or 2 digits 2 m Month as 2 digits 02 F Month February M Month as 3 letters Feb j Day of the month as 1 or 2 digits 8 d Day of the month as 2 digits 08 l (lowercase L) Day of the week Monday D Day of the week as 3 letters Mon w Day of the week as a single digit 0 (Sunday) z Day of the year: 0 to 365 189 t Number of days in the month 31 S English ordinal suffix for a day, as 2 characters rd as in 3rd g Hour; 12-hour format as 1 or 2 digits 6 G Hour; 24-hour format as 1 or 2 digits 18 h Hour; 12-hour format as 2 digits 06 H Hour; 24-hour format as 2 digits 18 i Minutes 45 s Seconds 18 u Microseconds 1234 a am or pm am A AM or PM PM U Seconds since the epoch 1154523600 e Timezone UTC I (capital i) Is it daylight savings? 1 (for yes) O Difference from GMT +0600 458 Appendix B Index Numbers 0666, explained, 302 0777 permissions, 330 Symbols //, using with comments, 24 /* and */, using with comments, 24, 26 /= assignment operator, 89 += assignment operator, 89, 457 -= assignment operator, 89, 457 *= assignment operator, 89 #, using with comments, 24 ?> tag, 9 short tags, 9 , using with comments, 25 + (addition) operator, 79, 135, 457 & (ampersand), using with forms, 68 && (and) logical operator, 135, 139, 457 * (assignment) operator, 89, 135 \ (backslash), using with strings, 39 & (bitwise) operator, 310 [] (brackets), using with keys in arrays, 161 {} (braces) versus parentheses (()), 172 using with conditionals, 143 using with if conditional, 125 . (concatenation) operator, 97, 135, 457 -- (decrement) operator, 88–89, 135, 457 / (division) operator, 79, 135, 457 $ (dollar sign) preceding variables with, 36, 58 printing, 82 \\ (double backslashes), using with absolute paths, 329 " (double quotation marks) effect of, 44–47 parse error generated by, 170 versus single quotation marks ('), 169 using with constants, 207 using with print, 17, 21 using with strings, 39 ' ' (empty string), using with functions, 284 / (equality) operator, 135 == (equality) operator, 135, 457 = (equals sign), using with variables, 41 > (greater than) operator, 135, 457 >= (greater than or equal to) operator, 135, 457 ++ (increment) operator, 88–89, 135, 457 != (inequality) operator, 457 % (inequality) operator, 135 < (less than) operator, 135, 457 <= (less than or equal to) operator, 135, 457 % (modulus) operator, 135, 457 * (multiplication) operator, 79, 135, 457 ! (negation) logical operator, 135, 457 ?? (null coalescing) logical operator, 135, 143 <=> (null coalescing) logical operator, 135, 143 | | (or) logical operator, 135, 139, 457 .. (parent folder), 303 () (parentheses) versus braces ({}), 172 using in calculations, 86–87 using with conditionals, 143 | (pipe), explained, 67 ; (semicolon) error related to, 65 using in MySQL client, 438 using with print command, 15 Index 459 ' (single quotation marks) using, 44 versus double quotation marks ("), 169 <=> (spaceship) operator, 135, 138, 457 - (subtraction) operator, 79, 135, 457 _ (underscore) using with forms, 51 using with functions, 270 using with variables, 37 A absolute paths, 203, 303, 329 access to pages, denying and troubleshooting, 405, 453 action attribute, including in forms, 50, 53, 57 add_entry.php document creating, 361–365 opening, 368 add_quote.php document creating, 306–309, 405–408 opening, 311–312 addition (+) operator, 79, 135, 457 addslashes() function, 370 administrator. See is_administrator() function Adobe Dreamweaver, 4 alphabetical sort, performing on arrays, 184 ALTER privileges, 446 ALTER SQL command, 346 AM or PM, formatting with date() function, 211, 458 am or pm, formatting with date() function, 211, 458 ampersand (&), using with forms, 68 AMPPS website, 428, 433 And (&&) logical operator, 135, 139, 457 AND logical operator, 135, 139, 457 Apache, 10 Aptana Studio, 4 arguments passing, 277 setting default values, 282–284 using with functions, 276–281 arithmetic, performing, 79–82 460 Index arithmetic operators, 89, 135, 457 array elements accessing, 161, 163, 170–172, 177 adding, 167–168 deleting, 166 entering, 165 pointing to, 173 array() function, 162–163 array values, printing, 171–172 arrays. See also multidimensional arrays adding items to, 166–169 creating, 162–165 creating from HTML forms, 186–190 deleting, 166 explained, 160 indexes and keys in, 161 merging, 169 parse errors, 170 printing, 164 versus scalar variable types, 160 sorting, 178–181 syntactical rules, 161 transforming between strings, 182–185 using, 40 asort() functions, using with arrays, 178–180 .aspx extension, 9 assignment operator, 89, 135 associative arrays, 40 Atom, 4 B backslash (\), using with strings, 39 basename() function, 329 binary digits, 310 birth year, creating input for, 123 Bitnami website, 428, 433 bitwise (&), 310 blank pages, troubleshooting, 452 section, creating, 5 $books multidimensional array, 174–176 books.php document, creating, 174–176, 208–209 bool type, 281 Boolean TRUE and FALSE, 121, 125, 131, 139, 395. See also false value braces ({}) versus parentheses (()), 172 using with conditionals, 143 using with if conditional, 125 brackets ([]), using with keys in arrays, 161 break language construct, 148 buffer size, setting, 236 C calculations, performing, 76–78 calculator1.php document creating, 286–289 opening, 293 calculator.html script, creating, 76–78 camel-hump and camel-case conventions, 37 case-sensitive searches, performing, 117 character set, setting for database, 392 characters, escaping, 62 checkboxes confirming, 142 creating for HTML form, 124 presetting status of, 227 closing tag, adding, 5 combined operators, 457 comments, adding to scripts, 24–26 comparison operators, 135–138, 457 concatenating strings, 97–100 concatenation (,) operator, 97, 135, 457 conditionals. See also nesting conditionals best practices, 143 explained, 121 nesting, 139 troubleshooting, 454 using functions in, 131 configuration changes, confirming, 437 configuring PHP, 436–437 constants. See also predefined constants benefits, 210 header.html file, 209 naming, 210 printing, 209–210 and superglobal arrays, 294 using, 207–210 control panel creating for directory, 326–329 viewing file permissions in, 301 control structures comparison operators, 135–138 default action, 132 die language construct, 150 else statement, 132–134 elseif statement, 144–147 HTML form for, 122–124 if conditional, 125–127 logical operators, 138–143 for loop, 152–156 switch conditional, 148–151 validation functions, 128–131 while loop, 156 $_COOKIE array, 251 cookie data, retrieving with PHP, 251–253 cookies adding parameters to, 254–256 checking for presence of, 395 comparing to sessions, 260–261 creating, 246–250 data limitation, 250 debugging, 244 deleting, 257–259 encoding values of, 253 expiration value, 254–255 explained, 244–245 httponly argument, 255 path and domain arguments, 254–256 reading from, 251–253 security issues, 245, 252, 255 sending, 247–250 setting expiration date, 255–256 testing safety of, 250 transmitting and receiving, 245 using tabs and newlines with, 252 using to identify administrators, 393 copying files on servers, 324 count() function, using with arrays, 167 CREATE DATABASE command, 445, 447 CREATE privileges, 446 CREATE SQL command, 346 CREATE TABLE SQL command, 356–357 create_table.php document, creating, 357–359 creating documents, 4 CSS (Cascading Style Sheets) basics, 3 font size and color, 251 Index 461 css folder, creating, 204 CSS templates, 200. See also templates CSV (comma-separated values) format, 338 customize.php document creating, 247–250 opening, 255 Cut and Paste, using with templates, 199 D database connections, making, 348–351 database information, best practices, 351 databases. See also MySQL databases; query data connection code, 359, 392 defined, 346 deleting data in, 376–381 inserting data into, 360–365 permissions, 352 resources, 450 retrieving data from, 371–375 updating data in, 382–387 date and time functions table, 458 working with, 211–213 date() and time() functions table, 458 using, 211–213, 254 using with sessions, 265 DateTime class, 213 day pull-down menu, creating, 272 daylight savings, formatting with date() function, 211, 458 days, formatting with date() function, 211, 458 $dbc conditional, 348, 359 DBMS (database management system), 345, 347 debugging PHP scripts, 440 steps, 27–28 decrement (--) operator, 88–89, 135, 457 decrementing numbers, 88–89 decrypting data, 112 default argument values, 282–284 default case, using with switch conditional, 151 DELETE FROM tablename query, 381 462 Index DELETE privileges, 446 DELETE query, running on databases, 376–381 DELETE SQL command, 346 delete_entry.php script, writing, 376–381 delete_quote.php document, creating, 418–421 deleting arrays and array elements, 166 cookies, 257–259 data in databases, 376–381 files, 324 quotes, 418–421 sessions, 266–267 delineated format, explained, 338 denying access to pages, 405 deprecated function, explained, 20 die() and exit() functions, 354 directories. See also web root directory creating, 330–337 displaying contents of, 326–327 navigating, 325–329 permissions, 302 directory control panel, creating, 326–329 dirname() function, 329 display_errors setting using, 63–64 using with cost calculator, 80 using in debugging, 28 division (/) operator, 79, 135, 457 documents, creating, 4 dollar sign ($) preceding variables with, 36, 58 printing, 82 double backslashes ( \\), using with absolute paths, 329 double quotation marks (") effect of, 44–47 parse error generated by, 170 versus single quotation marks ('), 169 using with print, 17, 21 using with strings, 39 double-precision floating-point numbers, 38 doubles, 38 DROP SQL command, 346, 446 drop-down menu, creating for HTML form, 124 E Edit menu, accessing for templates, 199 edit_entry.php document, creating, 383–387 edit_quote.php document, creating, 412–417 else statement, 132–134 elseif statement, 144–147 email, sending, 228–232 email address creating inputs for, 123 validating, 129 empty() function, 128, 131 empty string (' '), using with functions, 284. See also strings encoding explained, 5 external files, 206 encrypting data, 112 passwords, 337 ENTRIES table, columns in, 356 equality (/ and ==) operator, 135, 457 equals sign (=), using with variables, 41 error codes for files, 317 Error level, 65 error messages. See also parse errors; troubleshooting Add a Blog Entry, 364 arguments, 277 connection attempt refused, 10 Could not connect to the database, 350 Could not create the table, 358 Delete an Entry, 381 displaying in scripts, 63–64 double quotation marks ("), 21 email address and password, 402 foreach loop, 176 functions, 275 header() call, 233 include() function, 201 nonexisting variables, 61 Not Found, 14 output buffering, 233 permission denied, 299 for registration results, 142 related to color selection, 147 related to external files, 201, 206 related to header() call, 233 require() function, 201 setcookie() function, 246 trusting, 28, 451 unassigned value, 72 undefined function call, 275 Undefined variable, 43 error reporting, 65–67 error suppression operator, 354 error_reporting levels and constants, 65–67 event.html document, creating, 186–187 event.php document, creating, 188–190 everyone permission, 298, 301 exclusive or (XOR) logical operator, 139 execute permission, 298 exit() and die() functions, 237, 354 explode() function and fgets(), 338 using with arrays, 182, 184 external files. See also file extensions benefits, 206 closing PHP tag, 206 using, 201–206 writing to, 306–309 F FALSE and TRUE, 121 false value, 19. See also Boolean TRUE and FALSE fclose() function, 305 feedback.html document creating, 51 opening, 56 feof() function, 338 fgetcsv() function, 338, 342 fgets() function, 338, 348 file error codes, 317 file extensions. See also external files being aware of, 9 and included files, 206 file() function, 313, 338 file navigation, 203 file paths, 303 file permissions, 298–302, 352 FILE privileges, 446 file uploads, handling, 316–324 Index 463 FILE_APPEND constant, 303–304 file_exists() function, 300 file_get_contents() function, 313 fileatime() function, 329 filemtime() function, 328 filename() function, 325 fileperms() function, 329 files. See also saving documents and scripts copying on servers, 324 deleting, 324 locking, 310–312 organizing, 204 reading from, 313–315 reading incrementally, 338–342 writing to, 303–309 $_FILES array, elements of, 317 filesize() function, 328 filter() function, 131 finfo_file() function, 329 firewalls, 429 first name, checking entry of, 223 flag variable, creating for sticky form, 222 float type, 281 floating-point numbers, 38 flock() lock types, 310 folders and files, organizing, 204 font size and color, setting in CSS, 251 footer, adding to template, 197 footer file, creating for template, 200 footer.html document creating, 398–399 opening, 212 fopen() function, 305, 348 for loop, 152–156 using with functions, 272 using with numerically indexed arrays, 172 foreach loop error generated by, 176, 189 using with array elements, 170–172 using with directory control panel, 328 using with functions, 272 using with multidimensional arrays, 177 form data. See also HTML forms; sticky forms accessing, 62 displaying, 62 processing, 217 receiving in PHP, 58–62 464 Index sending to pages manually, 68–72 validating, 128–131 form methods, choosing, 54–57 form submission, determining, 214–215 form tags, 50 creating, 122 using with functions, 274 formatting numbers, 83–85 forms. See HTML forms forums, 96 frameworks, 455–456 function keyword, 271 function_exists() function, 275 functions. See also PHP functions; undefined functions; user-defined functions accessing, 281 arguments, 276–281 with arguments and value, 287 best practice, 275 calling without arguments, 282 creating and calling, 272–275 default argument values, 282–285 defining with parameters, 276–277 design theory, 295 error related to, 65 invoking, 271 looking up definitions of, 18–20 naming conventions, 270 return statement, 285 returning values, 285–289 syntax, 275–276 user-defined syntax, 270–271, 275 using spaces with, 85 using within conditionals, 131 functions.php script code, 397 creating, 394–395 fwrite() function, 305, 348 G garbage collection, 267 A Gentle Introduction to SQL website, 450 $_GET and $_POST, 55–62, 68 $_GET array, 161 GET method, using with HTTP headers, 240 getrandmax() function, explained, 91 Git version control software, 11 glob() function, 329 global statement, 290–294 GMT difference, formatting with date() function, 211–212, 458 GRANT privileges, 446–448 greater than (>) operator, 135, 457 greater than or equal to (>=) operator, 135, 457 $greeting variable, 97 grocery list array, 160 H handle_form.php document creating, 59 opening, 66 handle_post.php document creating, 79–82, 98–99 opening, 84, 86, 88, 101, 106, 109, 115, 118 handle_reg.php document creating, 126–127 opening, 129, 132, 136, 140, 145, 149 hash, 40 tag, creating, 5 header file, creating for template, 198–199, 203 header() function and HTTP headers, 237–240 and output buffering, 233 using exit with, 150 header lines, creating, 4 header.html document creating, 396–397 opening, 209, 234 headers already sent error, troubleshooting, 453 headers_sent() function, 240 Hello, World! greeting, sending to browser, 2, 16–17 hello1.php document creating, 16–17 opening, 21 hello2.php document creating, 21-22 opening, 25 hello.html script, creating, 69–70 hidden extensions, being aware of, 9 hidden input, checking for, 219 home page, creating, 422–425 hours, formatting with date() function, 211, 458 HTML (Hypertext Markup Language) current version, 2 resources, 6 sending to browsers, 21–23 syntax, 2 HTML comments, accessing, 26 .html extension, 9 HTML forms. See also form data; sticky forms control structures, 122–124 for cookies, 249 creating, 50–53 creating arrays from, 186–190 displaying and handling, 214, 216–219 event.php page, 187–190 handling, 59–61 handling with PHP, 214–219 hidden type of input in, 62 making sticky, 220–227 for numbers, 76–78 radio-button value, 62 re-displaying, 219 for strings, 94–96 for strings and arrays, 183–185 HTML pages creating, 4–6 example, 6 versus PHP scripts, 7 viewing source, 23 HTML source code, checking, 28 HTML tags addressing in PHP, 106–107 using PHP functions with, 104–107 tag, adding, 5 HTML5, 2 htmlentities() function, 384–385 htmlspecialchars() function, 328 HTTP (Hypertext Transfer Protocol), 237 HTTP headers, manipulating, 237–240 I id primary key, 387, 391 if conditional, 121, 125–127, 140 Index 465 if-else conditional, 132–134, 143 if-elseif conditionals, simplifying, 148–150 if-elseif-else conditional, 144–147 IIS (Internet Information Server), 10 implode() function, using with arrays, 182, 184 K keyboard shortcuts Cut and Paste, 199 Edit menu, 199 ksort() functions, using with arrays, 178–180 include() function failure of, 201 and parentheses (()), 206 using with constants, 207 using with external files, 202 increment (++) operator, 88–89, 135, 457 index errors, troubleshooting, 452 INDEX privileges, 446 indexed arrays, 40, 165 index.php document, creating, 202–205, 423–425 inequality ( % ) operator, 135 inequality (!=) operator, 457 ini_set() function, 263 INSERT INTO tablename SQL command, 360, 363 INSERT privileges, 446 INSERT SQL command, 346 installation on Mac OS X, 433–435 on Windows, 428–432 int type, 281 integers, 38 invalid MySQL argument error, troubleshooting, 453 is_administrator() function, 394, 406 is_array conditional, 189 is_dir() function, 325 is_file() function, 325 is_numeric() function, 128, 131 is_readable() function, 315 isset() function, 128, 131 J JavaScript, 105, 456 join() function, 185 JQuery website, 456 466 Index L language constructs, 150 languages. See multilingual web pages Laravel PHP framework, 455 leap year, formatting, 458 legacy file writing, 305 less than (<) operator, 135, 457 less than or equal to (<=) operator, 135, 457 linking strings, 100 links using to pass values, 68–69 using with multiple values, 72 list() function using with array elements, 189 using with functions, 288 list_dir.php document, creating, 326–329 list_dir.php script, 325 list.html document, creating, 183 list.php document, creating, 184–185 local variables, 97, 290 locking files, 310–312 $loggedin variable, 339, 341 logical operators, 135, 138–143, 457 login form, displaying, 218–219 login page HTTP headers added to, 240 purpose of, 216–217 login.php document creating, 216–219, 266–267, 338–342, 400–404 opening, 238, 262 loops nesting, 156 troubleshooting, 454 ltrim() function, 119 M Mac OS X Get Info panel, 302 installation on, 433–435 installing XAMPP on, 434–435 Magic Quotes, 62 mail() function, 228–230, 232, 437 make_date_menus() function, 274 make_text_input() function, 279, 295 MAMP website, 433 MariaDB, installation by XAMPP, 429 math. See arithmetic memory allocation, error related to, 65 menus.php document, creating, 272–274 merging arrays, 169 messages, printing, 16 meta tags, using for encoding, 5 method attribute, using with forms, 54–57 microseconds, formatting with date() function, 211 microseconds parameters, formatting with date() function, 458 minutes, formatting with date() function, 211 modulus ( % ) operator, 135, 457 money_format() function, using with numbers, 85 month pull-down menu, creating, 272 month values, formatting, 458 monthly payment, calculating, 81 months, formatting with date() function, 211 move_uploaded_file() function, 317, 319–320 Mozilla Developer Network website, 456 mtrand() function, using, 90–91 multidimensional arrays, creating, 40, 173–177. See also arrays multilingual forums, 96 multilingual web pages, creating, 5 multiplication ( * ) operator, 79, 135, 457 myblog database, 349 myquotes database, 390 MySQL client debugging PHP scripts, 440 using, 438–440 using semicolon (;) in, 438 on Windows, 440 MySQL database management system (DBMS), 345 MySQL databases. See also databases; tables apostrophes (') in form data, 370 connecting to, 348–351 creating, 445, 447 creating tables, 355–359 error handling, 352–354 inserting records into, 365 localhost value, 351 myblog, 349 queries and query results, 347 sending SQL statements to, 346 support in PHP, 346 username and password values, 349 MySQL users creating, 445–448 privileges, 445–448 root user password, 443–445 mysqli_affected_rows() function, 380, 387 mysqli_connect.php document creating, 348–350, 392 opening, 353 mysqli_error() function, 352–354 mysqli_fetch_array() function, 371–372, 375 mysqli_num_rows() function, 375, 387 mysqli_query() function, 346, 357, 371, 379 mysqli_real_escape_string() function, 367–370, 383, 385, 387 N name value, using to print greetings, 70–72 $name variable, creating via concatenation, 99 names, concatenating, 100 natsort() functions, using with strings, 181 navigating directories, 325–329 files, 203 negation (!) logical operator, 135, 457 nesting conditionals, 139, 217–218. See also conditionals nesting loops, 156 newlines (\n) converting to breaks, 101–103, 107 using, 22 using with cookies, 22, 252 Nginx, 10 Index 467 nl2br() function looking up, 19 using concatenation with, 100 using with newlines, 102 nobody permission, 302 Not Found response, receiving, 14 Notice error level, 65 NULL, using with functions, 284 null coalescing (??) logical operator, 135, 143 null coalescing (<=>) logical operator, 457 number_format() function, using, 83–85 numbers. See also random numbers creating HTML form for, 76–78 formatting, 83–85 incrementing and decrementing, 88–89 types of, 38 valid and invalid, 38 numeric indexes setting, 165 using for loop with, 172 O ob_clean() function, 234, 236 ob_end_flush() function, 234–237 ob_flush() function, 236 ob_get_contents() function, 236 ob_get_length() function, 236 ob_start() function, invoking, 233–234 octal format, 302 $okay variable, using with control structures, 126–127, 129–130 OOP (object-oriented programming), 455 The Open Web Application Security Project website, 455 operator precedence table, 457 operators for arithmetic, 79 table, 457 or (| |) logical operator, 135, 139, 457 OR logical operator, 135, 139, 457 ORDER BY RAND() clause, 424 ordinal suffix, 458 organizing files and folders, 204 others permission, 301 output buffering, 233–236, 250 owner of file, explained, 298 468 Index P pages. See HTML pages parameters, defining functions with, 276–277 parent folder (..), 303 parentheses (()) versus braces ({}), 172 using in calculations, 86–87 using with conditionals, 143 Parse error level, 65 parse errors. See also error messages; troubleshooting avoiding, 170 double quotation marks ("), 58 receiving, 43 troubleshooting, 454 password values, validating, 136–137 password_hash() function, 112, 337 password_verify() function, 337 passwords encrypting, 337 entering in HTML form, 123 managing, 124 validating, 130, 224 permissions, 298–302, 309, 352 PHP configuring, 436–437 configuring for file uploads, 318–319 PHP code, storing, 236 .php extension, 9 PHP functions, using with HTML tags, 104–107. See also functions PHP manual, using, 18–20, 449 PHP scripts accessing, 14 adding comments to, 24–26 creating, 8, 70–71 debugging, 28, 440 executing, 9 versus HTML pages, 7 requesting, 215 running through URLs, 451 testing, 12–14 testing in browsers, 12–14 ) operator, 135, 138, 457 spacing of HTML code, displaying, 22 sprintf() function, using with numbers, 85 SQL (Structured Query Language), features of, 346–347 SQL commands, 346 SQL Course website, 450 SQL statements, sending to MySQL, 346 SQL.org website, 450 square brackets ([]), using with keys in arrays, 161 sticky forms, 220–221. See also form data; HTML forms sticky text inputs, creating, 278–281 sticky1.php document creating, 278–281 opening, 283 str_ireplace(), using with trim(), 118–119 string case, adjusting, 117 string type, 281 strings. See also empty string (' '); substrings checking formats of, 116 comparing, 113 concatenating, 97–100 counting backward in, 114 creating HTML form for, 94–96 encoding and decoding, 108–112 encrypting and decrypting, 112 indexed position of characters in, 114 linking, 100 performing case-sensitive searches, 117 replacing parts of, 117–119 transforming between arrays, 182–185 using, 39 strip_tags() function, 104, 107 stripslashes() function, using with Magic Quotes, 62 strtok() function, 113 strtolower() function, 218 A Study in Scarlett website, 455 Index 471 Sublime Text, 4 submit button, creating for HTML form, 124 substrings, finding, 113–116. See also strings subtraction (-) operator, 79, 135, 457 superglobals and constants, 161, 294 switch conditional, 121, 148–151 T tab (\t), using with cookies, 252 tables. See also MySQL databases creating, 355–360 primary keys, 355 using primary keys in, 387 tags. See HTML tags tax rate, calculating, 81 $tax variable, 293 template.html document creating, 195–197 opening, 198, 200 templates. See also CSS templates creating, 194 footer file, 200 header file, 198–199 layout model, 195–197 website project, 396–399 testing PHP scripts, 12–14 safety of sending cookies, 250 text, sending to browsers, 15–17 text area, presetting value of, 227 text file, creating for file permissions, 299–300 text input type, checking, 138 textarea form element adding to forms, 53 using with newlines, 101–102 time() and date() functions table, 458 using, 211–213, 254 using with sessions, 265 time zones formatting with date() function, 211–212, 458 setting for servers, 213 tokens, substrings as, 113 Transmit FTP application, 301 472 Index trim() function using in comparisons, 138 using with strings, 117–119 troubleshooting. See also error messages; parse errors access denied, 453 advice, 451 blank pages, 452 calls to undefined functions, 452 conditionals and loops, 454 headers already sent, 453 invalid MySQL argument, 453 parse errors, 454 preset HTML form values cut off, 454 undefined variable and index errors, 452 variables without values, 452 TRUE and FALSE, 121, 395 true value, 19. See also Boolean TRUE and FALSE TRUNCATE TABLE tablename query, 381 types, declaring, 289 U uasort() functions, using with arrays, 181 undefined functions, troubleshooting calls to, 452. See also functions Undefined index notice, 170 Undefined offset notice, 170 Undefined variable error, 43 underscore ( _ ) forms, 51 functions, 270 variables, 37 unlink() function, 324 UPDATE privileges, 446 UPDATE SQL command, 346, 382–387 upload_file.php document, creating, 319–324 uploaded files, renaming, 324 uploads folder, creating, 318 urlencode() function, 108–112 “user,” defining, 299 user-defined functions, 270–271, 275, 278, 288, 393–395. See also functions username, using on registration pages, 124 users folder, creating, 330 users.txt script, 339–340 UTF-8 encoding, 5–6 V validating, passwords, 224 validation functions, 128–131 value types, declaring, 289 values, assigning to variables, 135 $var variable, 291 var_dump() function, using with arrays, 165 variable errors, troubleshooting, 452 variable names, case sensitivity of, 36 variable scope explained, 290–292 global statement, 293–294 variables. See also predefined variables accessing, 42–43 arrays, 40 assigning values to, 135 avoiding referring to, 131 documenting purpose of, 37 error related to, 65 explained, 32 incrementing values of, 88–89 minimizing bugs, 37 naming conventions, 37 numbers, 38 referring to, 37 scalar and nonscalar, 41 strings, 39 syntax, 36–37 types of, 38–40 valid and invalid, 37 validating, 147 values, 41–43 warnings related to, 37 variables.php document, creating, 42–43 version control software, 11 view_blog.php document, 386–387 view_entries.php document, creating, 372–375 view_quotes.php document, creating, 314–315, 409–411 view_settings.php document, creating, 251–253 W W3Schools JavaScript pages, 456 SQL Tutorial website, 450 WAMP website, 428 Warning error level web pages. See HTML pages web root directory, 298. See also directories web server applications, 10. See also servers website project. See also site structure adding quotes, 405–408 administrator, 390 creating home page, 422–425 database connection, 392 deleting quotes, 418–421 denying access, 405 editing quotes, 412–417 file organization and structure, 391 footer.html document, 398 identifying goals of, 390 listing quotes, 409–411 logging in, 400–403 logging out, 404 myquotes database, 390 security, 390 template, 396–399 user-defined function, 393–395 websites Adobe Dreamweaver, 4 AMPPS, 428, 433 Apache, 10 Aptana Studio, 4 Atom, 4 Bitnami, 428, 433 Git version control software, 11 IIS (Internet Information Server), 10 JavaScript resources, 456 MAMP, 433 Nginx, 10 PHP frameworks, 455–456 PHP manual, 18 PhpStorm, 4 Project Euler, 455 security resources, 455 SQL resources, 450 Sublime Text, 4 WAMP, 428 Windows installers, 428 XAMPP, 428, 433 Index 473 welcome.html file, saving, 6 welcome.php document, creating, 238–240, 264–265 while loop, 152, 156, 338 white space, using, 22 whole numbers, 38 Windows installation on, 428–432 installing XAMPP on, 430–432 wordwrap() function, 107 write permission, 298, 301–302 writeable directory, creating, 318–319 writing to files, 303–309 X XAMPP command prompt, 439 files installed by, 429, 433 and firewalls, 429 installing on Mac OS X, 434–435 installing on Windows, 430–432 MariaDB, 429 website, 428, 433 XOR (exclusive or) logical operator, 135, 139, 457 XSS (cross-site scripting) attacks, 105 Y year pull-down menu, creating, 272 year values formatting, 211, 458 validating, 136–137, 141 Yii PHP framework, 455 474 Index

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