$this->m_childlist[$i] 是一个 treenode 对象,另贴1段46行:
$this->m_childlist[$count]= new treenode($row['postid'],$row['title'],....$row = $this->m_childlist[$i]->display($row, $sublist);
的作用是沿着树枝输出所有节点和叶子