private static function listSortBy($list,$field, $sortby='asc') {
        if(is_array($list)){
            $refer = $resultSet = array();
            foreach ($list as $i => $data)
                $refer[$i] = &$data[$field];
            switch ($sortby) {
                case 'asc': // 正向排序
                    asort($refer);
                    break;
                case 'desc':// 逆向排序
                    arsort($refer);
                    break;
                case 'nat': // 自然排序
                    natcasesort($refer);
                    break;
            }
            foreach ( $refer as $key=> $val){
                $resultSet[] = &$list[$key];
            }
            return $resultSet;
        }
        return [];
    }