What's the difference between mod_php4, mod_php, and php?

What distro are you running? RedHat hasn't had a mod_php module since RH5.2.
PHP 4.1.2 is PHP4. To see if it is working with your apache server:

In your web root folder (most likely /var/www/html for RH7.3)
vi index.php
<? phpinfo() ?>

Now if apache is running then point your browser to the machine

127.0.0.1/index.php

and see what comes up.

> What's the difference between mod_php4, mod_php, and php packages?
> As directed on page 30 of 'Beginning PHP4' I ran $rpm -q mod_php4 to which I
> was told 'no such package installed. I do, however, have php-4.1.2-7
> installed.
> Do I still need mod_php4? I found it at rpmfind.net. In fact I found all three
> above 'variations' of php-- php, mod_php and mod_php4.
> I wish I knew what each was used for to understand what I still need to
> install.