Have you ever wanted to add a guest book to your web site? Or show a web counter? Well, PHP is just the ticket to get started. PHP (short for PHP: Hypertext Processor, yet another geeky recursive name) is a widely used scripting language that is designed from the ground up to be used in web pages. When you include PHP code in a page, it is interpreted by the web server when the page is requested. The code itself doesn't make it to the user, but the result of it does. This allows you to put all sorts of dynamic content on your web site.

There are lots of online guides and books out there to teach you how to use PHP, but to get started, you must have PHP. Most guides start out by telling you to download and compile the PHP distribution. Well, there's no need for that, because it's already built into Mac OS X. All you need to do is hunt down two lines in your Apache configuration and uncomment them. These are the two lines to look for in /etc/httpd/httpd.conf:

# LoadModule php4_module libexec/httpd/libphp4.so
...
# AddModule mod_php4.c

Since these lines are commented out by default, we'll have to uncomment them in order to make PHP functional. Do so, and the lines should now look like this:

LoadModule php4_module libexec/httpd/libphp4.so
...
AddModule mod_php4.c

Once you make this change, the following configuration block in your httpd.conf file takes care of the rest of the necessary configuration, including setting the php file type handler and adding index.php to the list of index pages used:

<IfModule mod_php4.c>
 # If php is turned on, we repsect .php and .phps files.
 AddType application/x-httpd-php .php
 AddType application/x-httpd-php-source .phps

 # Since most users will want index.php to work we
 # also automatically enable index.php
 <IfModule mod_dir.c>
 DirectoryIndex index.html index.php
 </IfModule>
</IfModule>

Save the Apache configuration file, and restart the web server:

$ sudo apachectl restart
httpd restarted

Let's take a look at our Apache error log for a second to illustrate a simple yet helpful bit of information. Each time you start Apache, it spits out a single line that tells you everything started successfully. With a plain-vanilla Apache server, the line usually looks something like this:

[Wed Apr 14 23:53:56 2004] [notice] Apache/1.3.29 (Darwin) configured -- resuming 
normal operations

When you add a third-party module or feature (such as PHP, mod_perl, mod_ssl, etc.), Apache graciously makes mention of it in this startup line. If you just restarted the Apache web server now, take a look at the error log by typing the following command:

$ tail /var/log/httpd/error_log

You should see Apache wax poetic with this line:

[Sat Apr 17 00:50:20 2004] [notice] Apache/1.3.29 (Darwin) PHP/4.3.2 configured -- 
resuming normal operations

Apache tells us that PHP is enabled, but how do we really know for sure? Rather easily, actually. Create a file named index.php in your Sites directory, using the following as its contents:

<? phpinfo( )?>