$total = $db->query("SELECT COUNT(*) FROM `forum` WHERE `type`='m' AND `refid`='".$f['id']."' AND `close`!='1'")->fetchColumn();Вроде так
$total = $db->query("SELECT COUNT(*) FROM `forum` WHERE `type`='m' AND `refid`='".$f['id']."' AND `close`!='1'")->fetchColumn();