Basic Help

I am new to PHP but have been using ASP for years. What i am trying to do is: 1) take a querystring variable 2) set it as a session variable 3) redirect the page back on itself all of this is done so the user never sees the querystring var so it must change it address bar 4) access the session variable as a hidden form element The code that follows is code i tried to write but it doesn't seem to work <-----------------------> <? $qs = ""; session_start(); if($_SERVER['QUERY_STRING']!="" && $_Session("qs") != "") { $_SESSION["qs"] = $_SERVER['QUERY_STRING']; session_register("qs"); header("Location: http://localhost/PHP/registration_form.php"); } ?> <html> <? echo $_SESSION["qs"]; ?> </html> <------------------------------> among other problems if there is no querystring value at all it gives me an error in the if statement Any help would be appriciated Thanks in advance ~Logan