Array
(
    [0] => Array
        (
            [power_id] => 1
            [power_name] => 新闻管理
            [action_name] => News
            [parent_id] => 0
        )    [1] => Array
        (
            [power_id] => 2
            [power_name] => 添加新闻
            [action_name] => News#add
            [parent_id] => 1
        )    [2] => Array
        (
            [power_id] => 3
            [power_name] => 修改新闻
            [action_name] => News#edit
            [parent_id] => 1
        )    [3] => Array
        (
            [power_id] => 4
            [power_name] => 查看新闻
            [action_name] => News#look
            [parent_id] => 1
        ))转换成:::以power_id=parent_id为条件
                    power_name作为键名

array(
        新闻管理=>array(
              [power_id] => 4
              [power_name] => 添加新闻
              [action_name] => News#look
              [parent_id] => 1
        )
   )管理