Building a Database-Driven Web Site Using PHP and MySQL

Part 3: Getting Started with PHP

Last week, we learned how to use the MySQL database engine to store a list of jokes in a simple database (composed of a single table named Jokes). To do so, we used the MySQL command line client to enter SQL commands (queries). This week, we'll introduce the PHP server-side scripting language. In addition to the basic features we'll be looking at this week, this language has full support for communicating with MySQL databases.

Presenting PHP

As we've discussed previously, PHP is a server-side scripting language. This concept is not obvious, especially if you're just used to designing pages with HTML and JavaScript. A server-side scripting language is similar to JavaScript in many ways, as they both allow you to embed little programs (scripts) into the HTML of a Web page. In executing, such scripts allow you to control what will actually appear in the browser window in some way more flexible that what is possible using straight HTML.

The key difference between JavaScript and PHP is that, while the Web browser interprets JavaScript once the Web page containing the script has been downloaded, server-side scripting languages like PHP are interpreted by the Web server before the page is even sent to the browser. Once interpreted, the PHP code is replaced in the Web page by the results of the script, so all the browser sees is a standard HTML file. The script is processed entirely by the server. Thus the designation: server-side scripting language.

Let's look back at the today.php example presented in Part One:

<HTML>
<HEAD>
<TITLE>Today's Date</TITLE>
</HEAD>
<BODY>
<P>Today's Date (according to this Web server) is
<?php


  echo( date("l, F dS Y.") );

?>
</BODY>
</HTML>

Most of this is plain HTML. The line between <?php and ?>, however, is written in PHP. <?php means "begin PHP code", and ?> means "end PHP code". The Web server is asked to interpret everything between these two delimiters and convert it to regular HTML code before sending the Web page to a browser that requests it. The browser is presented with something like this:

<HTML>
<HEAD>
<TITLE>Today's Date</TITLE>
</HEAD>
<BODY>
<P>Today's Date (according to this Web server) is
Wednesday, June 7th 2000.</BODY>
</HTML>

Notice that all signs of the PHP code have disappeared. In their place, the output of the script has appeared and looks just like standard HTML. This example demonstrates several advantages of server-side scripting:

No browser compatibility issues. PHP scripts are interpreted by the Web server and nothing else, so you don't have to worry about whether the language you're using will be supported by your visitors' browsers.
Access to server-side resources. In the above example, we place the date according to the Web server into the Web page. If we had inserted the date using JavaScript, we would only be able to display the date according to the computer on which the Web browser was running. Now while this isn't an especially impressive example of exploiting server-side resources, we could have just as easily inserted some other information that would only be available to a script running on the Web server�information stored in a MySQL database running on the Web server computer, for example.
Reduced load on the client. JavaScript can significantly slow down the display of a Web page on slower computers, as the browser must run the script before it can display the Web page. With server-side scripting, this becomes the burden of the Web server machine to bear.

Basic Syntax and Commands

SitePoint.com is a fast growing Web Developer Community. Kevin Yank is the Editor of the SitePoint TechTimes, a fresh, technically oriented newsletter for the serious Webmaster.

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Building a Database-Driven Web Site Using PHP and MySQL