I had to set up a Wikimedia Wiki once, and it needs the same feature for certain directories for security reasons. I had to put the following lines in the virtual host container in my httpd.conf:
<Files ~ '.php$'>
Deny from all
Allow from none
<Files ~ '.phps'>
Allow from all
That's for Apche 1.3 and PHP4. If you use Apache 2.0, use
And don't forget to restart your Apache!