Just in case you're still having issues with using Apache and your Mac, DevArticles just might have something you'll want to see. In one of their latest, Using Apache and PHP on Mac OS X (nice, original title), they start you off right.

From the beginning, they note that, most of the time, Apache is already installed on your Mac (unless someone purposely uninstalled it). There is a trick to getting PHP working on it, however, since it doesn't come installed as active by default. They take the shared module path, loading the mod_php4.c, and restart the Apache server to get the PHP modules to work correctly.

Actually, this procedure is one of the easiest installs out there, as far as Unix-based OSes go. There have been some that I've seen that have had issues, just because they put the lines in the wrong places in the httpd.conf, but other than that, it follows in the Apple tradition of being nice and simple...