http authentication and php

I am trying to write a php script that will work around a http authentication that I do have access to. I am trying to do this so that a form process in my control panel can automatically have information sent to it from a form that a user will fill out. However, my problem is in trying to get PHP to automatically authenticate. for example: I want to be able to call a url like this: http://server.com/greendocks/locked/useradd.htm?user=blah&pass=blah but this url is behind a http authentication. Is it possible to have this url called by a php script? And the second part of the question is can I do this process so it is completely invisible to the user that this page has been called? Because of course I don't want to allow users to have access to everything in my control panel. Hopefully someone knows what I'm getting at. Thanks for any help you may be able to provide. Jeff