Gyorgy Fekete has provided what he calls a complete guide to PHP development on Mac OS X in a recent blog entry.
Finally, I switched entirely to Mac. It is a little frustrating that there is not a complete resource on how to set up a web development enviroment on Mac OS X. The majority of tutorials are outdated. I will try to write this guide as complete as possible.
The guide provides basic installation instructions for PHP, MySQL (XAMPP or MAMP), the configuration of these two packages, throwing XDebug in to help with your debugging, installing Subversion and picking out your IDE of choice. He also suggests a somewhat optional step - setting up a Windows virtual machine to be able to test things out cross-platform without the need for a separate machine.