1. 删除redis

 $Ranking = $this->Redis->_delete('lianmengname');

2. 读取readis缓存

 $Ranking = $this->Redis->_get('lianmengname');

3. 存redis

if(empty($Ranking)){
      $Ranking = $this->DoubleAct->selectRanking();
      $this->Redis->_set('lianmengname',json_encode($Ranking),1800);//缓存半小时
    }