I\'m new to mac os x. In the Windows XP world, there are packages available, like easyPHP, wampserver, uniformserver, that enable you to have a local webserver complete with php
Mac OS X is -- essentially -- Linux.
Mac OS X already contains Apache. Turn on file sharing and you'll turn on Apache.
You'll need to download and install MySQL for Mac OS X. http://dev.mysql.com/downloads/mysql/5.1.html
You'll need to edit the httpd.conf to enable mod_apache.