关于在CONTROLLER里面执行SQL的问题 [ 新手入门 ]

public function getMysqlVersion() {
  $db = Yii::app()->db; //you have to define db connection in config/main.php
  $sql = "select version()";
  $command = $db->createCommand($sql);
  $results　= $command->queryAll();
  foreach($results as $result){
    print_r($result);
  }
}

出现错误，

PHP Error

Undefined variable: results

E:\webTools\htdocs\openShop\public\protected\controllers\AdminController.php(91)

79     {
80         Yii::app()->user->logout();
81         $this->redirect(Yii::app()->homeUrl);
82     }
83     /**
84 85      */
86     public function getMysqlVersion() {
87         $db = Yii::app()->db; //you have to define db connection in config/main.php
88         $sql = "select version()";
89         $command = $db->createCommand($sql);
90 91         foreach($results as $result){
92             print_r($result);
93         }
94 
95     }
96 }

错误页上没有91行，程序中是有的，就是

$results　= $command->queryAll();这个。

请问，大家可以告诉我原因吗？