Installing PHP on Mac OS
Installing PHP is more than just installing the PHP source code on the system. Several libraries are also required to connect to databases, connect to GD, support XML, get LDAP access and so on. All these have to be installed manually on the machine. You can go through the painful process of manual installation and configuration or simply download and install a ready-made package from entropy.ch.
Unless you have very specific needs, you should use this package.