Working with the Primary Key . . . . . . . . . . . . . . . . . . . . . 419 Recognizing Foreign Keys . . . . . . . . . . . . . . . . . . . . . . . . 419 Building the Foreign Key List Box . . . . . . . . . . . . . . . . . . 420 Working with Regular Fields . . . . . . . . . . . . . . . . . . . . . . 420 Committing a Record Update . . . . . . . . . . . . . . . . . . . . . 420 Deleting a Record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422 Adding a Record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422 Processing an Added Record. . . . . . . . . . . . . . . . . . . . . . 425 Building a List Box from a Field . . . . . . . . . . . . . . . . . . . 426 Creating a Button That Returns Users to the Main Page . . . . . . . . . . . . . . . . . . . . . . . . 427 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427 Appendix A: Reviewing HTML and Cascading Style Sheets . . . . . . . . .on cd Appendix B: Using SQLite as an Alternative Data Source . . . . . . . . .on cd Index . . . . . . . . . . . . . . . . . . . . . . . . . . .429 xx C o n ten t s omputer programming has often been seen as a difficult and arcane skill. Programming languages are difficult and complicated, out of the typical person’s reach. However, the advent of the World Wide Web has changed that to some extent. It’s reasonably easy to build and post a Web page for the entire world to see. The language of the Web is reasonably simple, and numerous applications are available to assist in the preparation of static pages. At some point, every Web author begins to dream of pages that actually do something useful. The simple HTML language that builds a page offers the tan- talizing ability to build forms, but no way to work with the information that users type into these forms. Often, a developer has a database or some other dynamic information they wish to somehow attach to a Web page. Even languages such as JavaScript are not sat- isfying in these cases. The CGI interface was designed as an early solution to this problem, but CGI itself can be confusing and the languages used with CGI (espe- cially Perl) are very powerful, but confusing to beginners. PHP is an amazing language. It is meant to work with Web servers, where it can do the critical work of file management and database access. It is reasonably easy to learn and understand, and can be embedded into Web pages. It is as powerful as more-difficult languages, with a number of impressive extensions that add new features to the language. In this book, I teach you how to write computer programs. I do not expect you to have any previous programming experience. You learn to program using the PHP language. Although PHP itself is a very specialized language (designed to enhance Web pages), the concepts you learn through this language can be extended to a number of other programming environments. Whenever possible, I use games as example programs. Each chapter begins by demonstrating a simple game or diversion. I show you all the skills you need to write that game through a series of simple example programs. At the end of the chapter I show the game again, this time by looking at the code, which at that point you will understand. Games are motivating and often present special challenges to the pro- grammer. The concepts presented are just as applicable in real-world applications. I n t ro d u c t i o n C xxii I n t r o d u c t i o n This second edition adds new features and includes updates from the previous edition of the book. Specifically, it includes new chapters on object-oriented programming (OOP) and XML, as well as examples on using PHP to create content management systems. I’ve updated the code to reflect improvements in PHP 5.0, including the improved object model and XML tools, and the new SQLite data access tools. Programming is not a skill you can learn simply by reading about it. You have to write code to really understand what’s going on. I encourage you to play along at home. Look at the code on the accompanying CD. Run the programs yourself. Try to modify the code and see how it works. Make new variations of the programs to suit your own needs. W eb pages are interesting, but on their own they are simply documents. You can use PHP to add code to your Web pages so they can do more. A scripting language like PHP can convert your Web site from static document to an interactive application. In this chapter you learn how to add basic PHP functionality to your Web pages. You also learn how to do these things: • Download and install Apache • Download and install PHP • Configure Apache to recognize PHP 5.0 • Configure PHP to run extensions used in this book (including MySQL and XML) • Ensure PHP is on your system • Run a basic diagnostic check of your PHP installation • Add PHP code to a Web page E x p l o r i n g t h e P H P E n v i r o n m e n t 1 CHAPTER Introducing the Tip of the Day Program Your first program probably won’t win any Web awards, but it takes you beyond what you can do with regular HTML. Figure 1.1 illustrates the Tip of the Day page, which offers friendly, helpful advice. You could write this kind of page without using a technology like PHP, but the program is a little more sophisticated than it might look on the surface. The tip isn’t actually embedded in the Web page at all, but it is stored in a completely separate file. The program integrates this separate file into the HTML page. The page owner can change the tip of the day very easily by editing the text file that contains the tips. 2 P H P 5 /M y S Q L P r o g r a m m i n g f o r t h e A b s o l u t e B e g i n n e r FIGURE 1.1 The tip of the day might look simple, but it is a technological marvel. It features HTML, cascading style sheets, and PHP code. IN THE REAL WORLD The Tip of the Day page illustrates one of the hottest concepts in Web program- ming today: the content management system. This kind of structure allows programmers to design a Web site’s general layout, but isolates the contents from the page design. The page owners (who might not know how to modify a Web page directly) can easily change a text file without risk of exposing the code that holds the site together. You’ll learn how to build a full-blown content management system in chapter 8, “XML and Content Management Systems.” . basic PHP functionality to your Web pages. You also learn how to do these things: • Download and install Apache • Download and install PHP • Configure Apache to recognize PHP 5.0 • Configure PHP. used in this book (including MySQL and XML) • Ensure PHP is on your system • Run a basic diagnostic check of your PHP installation • Add PHP code to a Web page E x p l o r i n g t h e P H P E n v i r o n m e n t 1 CHAPTER Introducing. but on their own they are simply documents. You can use PHP to add code to your Web pages so they can do more. A scripting language like PHP can convert your Web site from static document to an interactive