basic: getting current URL

Hi, Is there a simple way to get the filename of the current page? I have a session test included at the top of each page that redirects the user to a login page if they are not logged in. I want to capture the URL they tried to access, so I can send them back there after they go to the login page and login. I think this should be simple, but I'm just not finding it. Thanks, Sam //get path of current page $current_url = HOW DO I GET THE PATH? // session check session_start(); if (!session_is_registered("SESSION")) { // if session check fails, invoke error handler header("Location: http://www.site.com/index.php?from_page=$current_url"); exit(); }