That would probably mean you either dont have PHP installed, or dont have it enabled. You can find if you have it installed by typing 'php -v' at the console, and you should get something along the lines of:
PHP 4.3.0 (cli) (built: Feb 16 2003 00:19:13)
Copyright (c) 1997-2002 The PHP Group
Zend Engine v1.3.0, Copyright (c) 1998-2002 Zend Technologies
If you have it installed, then it is not enabled for Apache. You can test it by (first making sure Apache isnt running) then typing apache -D php4
(as root) then accessing your PHP page. A good and simple way of doing it is to create a .php file with a single line of code: '<? phpinfo(); ?>
' - that should make lots of nice information for you, if it doesn then theres something wrong with your PHP installation and you need to give it another go, keeping an eye out for any errors.
If it does work, then you need to add the '-D php4' argument to your apache init script so it starts like that everytime. Now I dont know what distro you're running, but if theres an init config file for Apache (for example, in Gentoo theres /etc/conf.d/apache) then there should hopefully be an example in there to show you how to format it (ie: APACHE_OPTS="-D php4")