if($_GET[username])
{
    $_COOKIE[username] = $_GET[username];
    $_COOKIE[password] = md5($_GET[password]);
}

$result = dbquery("SELECT * FROM ".PREFIX."user WHERE username = '".$_COOKIE[username]."' AND password = '".$_COOKIE[password]."'");
$user = mysql_fetch_array($result);

if(!$user[id])
{
    header("Location: ./login.php?loc=".$_SERVER[REQUEST_URI]);
    exit;
}