Rob Allen: Setting up PHP & MySQL on OS X 10.8 Mountain Lion
Rob Allen has posted some notes to his site helping you get PHP set up on OSX Lion (10.8) successfully.
With OS X 10.8, Apple continues to ship PHP 5.3 with Xdebug, PEAR, GD and PDO_MYSQL. This is how to set it up from a clean install of 10.8.
He's broken it up into a few sections including the MySQL setup, Apache configuration, updating the main php.ini and setting up PHPUnit ("and friends") for your testing. He also includes setup instructions for the mcrypt and the PECL OAuth extensions.