数组排序，

$orderFile = array();
            $sort = array(
                ‘direction‘ => ‘SORT_DESC‘, //排序顺序标志 SORT_DESC 降序；SORT_ASC 升序
                ‘field‘     => ‘ctime‘,       //排序字段
            );
            foreach($list as $vo){
                $orderFile[]=$vo[‘lastTime‘];
            }
            array_multisort($orderFile ,SORT_DESC, $list);