apache not displaying php pages, offering them for download instead
You're missing a PHP script handler.
The configuration lines in Apache2 that you're missing look something like this:
# Use for PHP 5.x:
LoadModule php5_module modules/libphp5.so
AddHandler php5-script php
# Add index.php to your DirectoryIndex line:
DirectoryIndex index.html index.php
With something like Apache on Linux, it's typically installed when you include the PHP packages into your distribution.
What OS are you running this on?
You could also try this
a2enmod php5
then restart apache2 with
rcapache2 graceful
on a suse style linux