I had the same problem.
So I read an article on PHPmac.com, but before re-doing everything I just tried this:
If you have not used PHP on your Mac before:
Open the Apache Configuration file (/etc/httpd/httpd.conf) in your favourite Text Editor (In these examples I have used Pico)
% sudo pico /etc/httpd/httpd.conf
Now add these lines to the very bottom of the file:
AddType application/x-httpd-php .php
AddType application/x-httpd-php-source .phps
Now save and quit by pressing Control-O, Overwrite the old file (hit Enter) and then press Control-X to exit Pico.
% sudo apachectl restart
If you have any questions etc. please check below, or email email@example.com
That worked for me.
For the complete article goto http://www.phpmac.com/articles/view.php?id=117