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
Five years later, i believe this question and existing answers still reading by some newcomers.
Personally, i strongly recommend using Homebrew to have a perfect development environment on mac os x. Not only PHP, homebrew opens wide all the doors to the open source toolkit/library/application heaven.
Here is my another answer related with this subject.