请教一个Discuz X2中的帖子排序模式问题！

复制内容到剪贴板

代码:

function forumpost($fid,$num,$orderby,$messagenum,$typeid=0,$sortid=0){
$manylist=array();
require_once libfile('function/post');
if($typeid){
$typeadd=" and t.typeid in ($typeid)";
}
if($sortid){
$sortadd=" and t.sortid in ($sortid)";
}
$rs=DB::query("
SELECT t.*,p.message,p.pid,f.name
FROM ".DB::table("forum_thread")." t
LEFT JOIN ".DB::table("forum_post")." p on p.tid=t.tid
LEFT JOIN ".DB::table("forum_forum")." f on f.fid=t.fid
WHERE t.`fid` in ($fid) $typeadd $sortadd and t.displayorder>=0 and p.first=1
group by t.tid
ORDER BY t.`$orderby` DESC
LIMIT 0 , $num");
while ($rw=DB::fetch($rs)) {
$rw['lastposterenc']=urlencode($rw['lastposter']);
$rw['message']=messagecutstr($rw['message'],$messagenum,'');
$rw['message']=dhtmlspecialchars($rw['message']);
$manylist[]=$rw;
}
return $manylist;
}