Why is php not running?

I've seen this question answered many times, but most end either unanswered or by telling the asker to put this:

<?php phpinfo() ?>

in a test file. Obviously, if that produced what was expected, I wouldn't be here. Instead, I get a 404 error.

I'm using an ubuntu 12.04 server with Amazon. Apache is installed, php5 is installed, and apache was restarted. I followed the following sequence:

sudo apt-get install apache2sudo apt-get install php5sudo apt-get install libapache2-mod-php5sudo /etc/init.d/apache2 restart

Each one of the first three commands now gives me "apache2 is already the newest version.0 upgraded, 0 newly installed, 0 to remove and 3 not upgraded" Obviously, replace apache2 with php5 and libapache2-mod-php5 for the other two.

This is a sure way to tell me it's installed, correct? Well, when I use the command "top", php is not one of the services that are running, which tells me it's not running, correct?

Navigating to the IP address gives me Amazon's "It Works!" page, but navigating to any other page on the server produces a 404 error.

Any help is much appreciated.