In your apache’s httpd.conf you need these things
LoadModule php5_module modules/libphp5.so

DirectoryIndex index.php index.html
(inside the dir_module ifModule condition)

and, most importantly (and the one you probably missed:
AddType application/x-httpd-php .php

in the mime_module ifModule condition

I bet you use a sledgehammer for your screws, don’t you.