为什么activitieDropdownlist的值始终无法获取到？
视图层view

<form method="post">

          <?php echo CHtml::activeDropDownList($m_subjectlist,'subject_name',$sb_list);?>

 <div class="row submit">

     <?php echo CHtml::submitButton('显示我所选择的专业'); ?>

 </div>

 <?php  echo 'test'.$result.'111';?>

 </form>

控制器层

	public function actionDbdplist()

	{

    $m_subjectlist = new SubjectList();

    $m_gradelist = new Grade;

    $this->subject_list = SubjectList::model()->findAll(); 

    $this->grade_list = Grade::model()->findAll();                                         

	//使用findAll 得到的结果是数据对象所以这样小小处理一下吧他们转换成数组:

    foreach($this->subject_list as $item)

	{

         $sb_list[$item->subject_id] = $item->subject_name;

    }

    foreach($this->grade_list as $item)

	{

         $gd_list[$item->grade_id] = $item->grade_name;

    }







	$result=$_POST['subject_name'];

	



    $this->render('dbdplist',array(

               'm_subjectlist' => $m_subjectlist,

               'm_gradelist' => $m_gradelist,

               'subject_list'=>$this->subject_list,

               'grade_list'=>$this->grade_list,

               'sb_list'=>$sb_list,

               'gd_list'=>$gd_list,

               'result'=>$result,

		'model'=>$model,));

			  

 }