Just a tip for anyone looking to install php on a Mac, since there seems to be nothing here.
Yes it's true that an Apache server is included in OS X, but I always found problems with MySQL when using it.
Lets face it. Setting up a server can suck.
MAMP is your solution (http://www.mamp.info/).
MAMP stands for Mac Apache MySQL PHP and installs a second server utilising different ports so as not to disturb your current OS X one.
Comes all pre-configured with some nifty features and usual suspects such as phpMyAdmin.
Check it out, definately worth it to any Mac PHP developers.