Chapter V.4. PHP

In the old days, Web pages were used to display information, such as text and graphics. Nowadays, Web pages are dynamic, so they not only need to respond to the user, but they often need to retrieve information off a Web page and store it in a database, such as when you type your credit card number to buy something off a Web site.

HTML can create simple user interfaces, but when you need to transfer data from a Web page to another program, such as a database, you need to use a programming language. Although programmers have used C, Perl, and Java to link Web pages to other programs like databases, one of the most popular programming languages for this task is PHP, which is a recursive name that stands for PHP Hypertext Processor (

Although languages such as C and Perl can be used to create standalone applications, PHP programs are unique in that they can run only on Web pages. Not only is PHP designed for creating programs within Web pages, but PHP is also free and capable of running under many different operating systems. If you're already familiar with C and Perl, you'll find that PHP mimics much of the syntax from both languages. Although you can create dynamic Web sites with other programming languages, you may find PHP easier and simpler to use.

The Structure of a PHP Program

At the simplest level, a PHP program can consist of one or more commands embedded in a Web page's HTML code, such as

      echo "<h1>Greetings from PHP.</h1>";
?> ...

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