is their a way to run a command as root ???

Is their a way to run a command as root..or another user.. I know their are a log of security issues with allowing this.. I will tighten down security after I get it to work. He is what I am trying to do. I have squid & squid guard set up.. in squids redirect url.. (on the same box).. I would like to modify a checked/domain list (I'm currently doing this manually... though I think I know how to do this ..or at least the book I have does.) after it is modified I need to run the fallowing... --update-- #!/bin/sh ./squidguard -C all #or a specific db.. but all covers... all /etc/init.d/squid restart I can run this as root or as squid.. I did create a test script which just copied some files in the /tmp dir.. --test-- #!/bin/sh echo "this is a test" cp /usr/local/httpd/htdocs/Block.html /tmp/Block.html I can run this.. and it works with the fallowing.... <?php $command="./test"; system($command); ?>