External Login Code Security Question

[citricguy]

I'm working on a script that uses GET variables to handle logins from non vb pages that redirect back to non vb pages after getting a user to log in.

I'm fairly novice at coding PHP and wanted to see if you guys could help me secure this doc.

PHP Code:

<?php
//Load global.php
require_once('./global.php');

//Clean GET variabls
$vbulletin->input->clean_array_gpc('g', array(
'r' => TYPE_NOHTML,
'g' => TYPE_UINT
)); 

//Login and Redirect
if (!is_member_of($vbulletin->userinfo, $vbulletin->GPC['g']))
{
    print_no_permission();
} else {
    header("Location:". $vbulletin->GPC['r']) ;
}
?>