zhangjingyu 
检索最后回帖时间字段名lastpost，thread.php文件中这段应该提到了时间：
function getThreadMethod() {
global $page,$db_fcachenum,$fid,$foruminfo,$timestamp,$db_fcachetime;
$fcache = 0;
if ($db_fcachenum && $page threadSearch->urladd)) {
$fcachetime = pwFilemtime(D_P . "data/bbscache/fcache_{$fid}_{$page}.php");
$lastpost = explode("\t", $foruminfo['lastpost']);
if (!file_exists(D_P."data/bbscache/fcache_{$fid}_{$page}.php") || $lastpost[2]>$fcachetime && $timestamp-$fcachetime>$db_fcachetime) {
$fcache = 1;
} else {
$fcache = 2;
}
}
return $fcache;
}