What's your http.conf file look like? Did you make the necessary additions for .php file types?
AddType application/x-httpd-php .php
I run the generic Apache 1.3.26 debian package that comes on stable, but I remember having a hard time with Apache 2 when it first came out. I gave up and stuck with the old version.
Just searching Google I found this page that might give you some help:
http://dan.drydog.com/apache2php.html