Redirect without changing url ?

If somebody logs in on say myserver/login.php, then if login is ok there are redirected to their page say myserver/joe.php

Well how do i have it so it goes,

login.php--->main.php but still on their page, so there could be 10 users, each with their own page but all they see is main.php, in other words i want to stop direct access to an individual page, if it was just myserver/joe.php then you could directly acces that page. I know you cause sesions and cookies to check if the've logged in or not but how do you hide the url?

I'm confused :(

Can you explain in steps what you want the result to be when the user does exactly what?

Well why dont you just check the HTTP_REFER in the joe.php file and if it hasnt come from login.php. Alternativly you could just use include in the main.php file to include the current users file. Hope that makes sense