frost, вот, вынудил
static function online()
{
$users = mysql_result(mysql_query("SELECT COUNT(*) FROM `users` WHERE `lastdate` > '" . (time() - 300) . "'"), 0);
$guests = mysql_result(mysql_query("SELECT COUNT(*) FROM `cms_sessions` WHERE `lastdate` > '" . (time() - 300) . "'"), 0);
$b = $users + $guests;
return (core::$user_id || core::$system_set['active'] ? '<a href="' . core::$system_set['homeurl'] . '/users/index.php?act=online">Онлайн: ' . $b . '</a>' : core::$lng['online'] . ': ' . $users . ' / ' . $guests);
}