PHP stopped rendering in Apache

[jeebus]

I searched the forum but did not find a solution.

I am a novice in Linux/Unix attempting to install snort on a computer. Initially php was rendered properly. As I progressed with the installation and moved to configuring BASE (

http://secureideas.sourceforge.net/),

connecting to the machine with "

http://IP-address"

and "

http://IP-address/base",

apache showed the text of the php file, as in:

<?
########################################################################
# nqt.php last revised 02/19/05 (

http://www.shat.net/php/nqt/)

#
# Initial release 03/11/01 #
# NQT is now nearly four years old and still in wide use! #
# #
# Copyright (C) shaun@shat.net. Full license follows update
...

How do I get Apache to render php properly again and use index.php as one of its default pages?