數組根據一個字段排序

function sort_list($list, $field, $count, $sortby = 'desc'){
        $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;
        }
        $resultSet = new stdClass();
        foreach ($refer as $key => $val)
        {
            $resultSet->data[] = &$list[$key];
        }
        return $resultSet;
    }