URI Segments and payment gw

[eluser]learnq[/eluser]
not clear why it is not working as you said

Code:

class Auth extends Controller {  
    
function __construct()
       {
            parent::Controller();
       }

function payment($name,$pass)
{
    echo 'here'  ;

    
     $query_string = $this->input->server('QUERY_STRING',TRUE);
$vars = explode('&',$query_string);
print_r($vars);
$get = array();
foreach($vars as $var){
    list($key,$value) = explode('=',$var);
    $get[$key] = urldecode($value);
}



}
    
}

http://mysite.com/auth/payment

it shows 'here'

but
http://mysite.com/auth/payment?Parameter...MPQu9P04S6

says

404 Page Not Found