I have been using snow leopard and recently I got a new mac with mountain Lion. As a PHPer the first thing I was doing was to install php+mysql and I have found it much easier
here is how to enable apache for PHP:
1. go to terminal, click the launch icon from dock and you will find it in the utilities, and do
apachectrl start – you need a sudo access for this
2. Go to system preferences -> internet and wireless -> sharing and check web sharing
3. Now, go to http://localhost and verify the it works is there.
4. Then being on your editor, go to /etc/apache2 and open httpd.conf file. Then look for php5_module and uncomment that line.
5. You are done. For testing, go to /Library/Webserver/Documents/ and add a php file named phpinfo.php with content of phpinfo(); and access it from http://localhost/phpinfo.php
Happy PHP