Restrict PM's to Usergroups update auf 1.6??

PHP-Code:
<?php

function pmrestrict_info()
{
        return array(
                "name"          => "Restrict PM's to Usergroups",
                "description"   => "disallows to send a pm to somebody within a different usergroup",
                "website"       => "http://www.mybbcoder.info",
                "author"        => "XxAnimusxX",
                "authorsite"    => "http://www.mybbcoder.info",
                "version"       => "2.0",
        );
}


$plugins->add_hook("private_send_do_send", "checkUsergroups");
function checkUsergroups()
{
global $db, $mybb;

$admin_allow = array(3,4,6,10,11);
if (in_array($mybb->user[usergroup], $admin_allow)) return true;

$query = $db->simple_select("users", "uid", "username='".$db->escape_string($mybb->input['to'])."'", array("limit" => 1));
$user = $db->fetch_array($query);
$toid = $user['uid'];

if (!$toid)
{
return false;
}

$query = $db->write_query("SELECT g.gid FROM ".TABLE_PREFIX."users u LEFT JOIN ".TABLE_PREFIX."usergroups g ON (u.usergroup = g.gid) WHERE u.uid = $toid");
$receipient = $db->fetch_array($query);

$allow = array(3,4,6,10,11);
if ($receipient[gid] != $mybb->user[usergroup] && !in_array($receipient[gid], $allow))
{
error("Es ist Ihnen nicht erlaubt eine Person ausserhalb Ihrer Benutzergruppe anzuschreiben.");
}
}

?>