Hypertext Pre-processor: What is PHP?

What is PHP?

Hypertext Pre-processor  (PHPs) is a  server-side scripting language, and  server-sidescripts are special commands you must place in Web pages. Those commands are processed before the pages are sent from your Server to the Web browser of your visitor. A typical PHP files will content commads to be executed in the server in addition to the usual mixture of text and HTML (Hypertext Markup Language) tags.

When you type a URL in the Address box or click a link on a Web page, you're asking a Web server on a computer somewhere to send a file to the Web browser (sometimes called a "client") on your computer. If that file is a normal HTML file, it looks exactly the same when your Web browser receives it as it did before the Web server sent it. After receiving the file, your Web browser displays its contents as a combination of text, images, and sounds. In the case of an PHP page, the process is similar, except there's an extra processing step that takes place just before the Web server sends the file. Before the Web server sends the PHP file to the Web browser, it runs all server-side scripts contained in the page. Some of these scripts display the current date, time, and other information. Others process information the user has just typed into a form, such as a page in the Web site's guestbook

To distinguish them from normal HTML pages, PHP files are usually given the ".php" extension.

What Can You Do with PHP?

There are many things you can do with PHP.

What Do PHP pages Look Like?

The appearance of an PHP page depends on who or what is viewing it. To the Web browser that receives it, an Active Server Page looks just like a normal HTML page. If a visitor to your Web site views the source code of an PHP page, that's what they see: a normal HTML page. However, the file located in the server  looks very different. In addition to text and HTML tags, you also see server-side scripts. This is what the PHP page looks like to the Web server before it is processed and sent in response to a request.

What Do PHP pages Look Like?

Server-side scripts look a lot like HTML tags. However, instead of starting and ending with lesser-than ( < ) and greater-than ( > ) brackets, they typically start with <?php or <? and will typically end with ?>. The <?php or <? are called anopening tags, and the ?> is called a closing tag. In between these tags are the server-side scripts. You can insert server-side scripts anywhere in your Web page--even inside HTML tags.

Do You Have to Be a Programmer to Understand Server-Side Scripting?

There's a lot you can do with server-side scripts without learning how to program. For this reason, much of the online Help for PHP is written for people who are familiar with HTML but aren't computer programmers.