Installing the App Engine SDK for PHP on Mac OS X
The SDK includes software for a web server that you can run on your own computer to test your PHP applications. It also includes software to upload your application to App Engine when you are done testing it locally.
The download link for the PHP SDK for Mac OS X is: http://googleappengine.googlecode.com/files/GoogleAppEngineLauncher-1.8.8.dmg
Verifing Python 2.7
The App Engine PHP SDK requires Python 2.7, which is installed by default on Mac OS X 10.6 (Lion) or later. You can verify your Python installation using the following command:
/usr/bin/env python -V
If the output looks like Python 2.7.<number> then you already have the correct Python version installed. Otherwise you can download and install Python 2.7 from the Python web site.
Installing MySQL
Most PHP apps use a MySQL backend, which is not packaged with the App Engine SDK. To setup MySQL, visit the MySQL Downloads page; the "Community Server" edition will suffice for your local development.
Next...
Once you have the SDK and MySQL installed, continue to Hello, World! to start writing some code