zhangjingyu 
继续楼上查看（以“hotfavor”搜索），果然是和第12行hotfavorUpdate有关，这里应该是重点。
lib/elementupdate.class.php
    function hotfavorUpdate($tid, $fid) {
        if (!($this->ifcache & 1024) || !$tid || !$fid) {
            return false;
        }
        $eid = $this->db->get_value("SELECT eid FROM pw_elements WHERE type='hotfavor' AND mark=" . S::sqlEscape($fid) . " AND id=" . S::sqlEscape($tid));
        if ($eid) {
            $this->db->update("UPDATE pw_elements SET value=value+1 WHERE eid=" . S::sqlEscape($eid));
        } else {
            $rt = $this->db->get_one("SELECT favors FROM pw_threads WHERE tid=" . S::sqlEscape($tid));
            $rs = $this->db->get_one("SELECT value,eid FROM pw_elements WHERE type='hotfavor' ORDER BY value ASC");

            if ($rt['favors'] > $rs['value']) {
                $this->db->update("DELETE FROM pw_elements WHERE eid=" . S::sqlEscape($rs['eid']));
                $favors = array(
                    'id' => $tid,
                    'mark' => $fid,
                    'value' => $rt['favors'],
                    'type' => 'hotfavor'
                );
                $this->db->update("REPLACE INTO pw_elements SET" . S::sqlSingle($favors, false));
            }
        }
        return true;
    }
还有点没看明白，稍后再研究。继续。