add groups to linux with apache + php

Hi everybody, Maybe this is not the exact place for this post, as is more a problem with permissions and linux, but I have been searching all around and I cannot find an answer to my problem, so if somebody can lend a hand it will be greatly appreciated. My problem is that i have written a script that only adds a group to linux with function groupadd and with a name that i give in a php page. If I execute the script from console, it works fine, as I am root user on my machine, but when I try to execute from web page, it makes nothing, as the user is apache. If I want to make su at the beginning of the script, is it possible to send also the password so it prompts for nothing? is there a better way to do that? I'm using RH9, Apache 2 and php 4.2.3. Thx in advance.