This is probably due to the server-setting "register-global" is set to off.
All posted variables to the page and all server variables are no langer available as a "normal" variable.
You will have to use $_POST, $_GET, $_SESSION, $_COOKIE and $_SERVER
see http://www.php.net/manual/en/reserved.variables.php for more details on wich you can find where and why.
Greetz Daan
