I just recently set Apache up on my home server (more on the server at some point in the future), but I was having problems serving up php pages. Every time I tried to access a php based page, Firefox came up asking if I wanted to download a ‘.PHTML’ file!!! 
Thankfully the answer (like most things with Ubuntu) was found on the Ubuntu Forums…
Simply edit the file /etc/apache2/apache2.conf by adding the following line:
AddType application/x-httpd-php .php .phtml
Now php files should be handled by the server in the way that they were intended.