how to change values in a dropdown list using ajax in Yii

controller.php

public function actionMysubcategory(){
    $model = new YourModel();
    $cid = Yii::app()->request->getPost('cid'); 
    $subcategory= Subcategory::model()->findAll(
            array('order'=>'sid',
           'condition'=>'cid=:cid', 
           'params'=>array(':cid'=>$cid)));
        $list = CHtml::listData($subcategory, 
        'sid', 'sname');
       echo CHtml::activeDropDownList($model,'sid',$list);
} 

view.php

<?php
       $list = CHtml::listData($category, 
            'cid', 'cname');    
       echo $form->dropDownList($model,'cid',$list,
             array('empty' => '(Select a category)')); 
?> 
<label>Sub Category *</label>

 <div id="sub-category-wrapper">
 <?php  
      $subcategory = array();
      echo $form->dropDownList($model,'sid',$subcategory,
          array('empty' => '(Select a subcategory)')); 
  ?>
</div>


<?php
Yii::app()->clientScript->registerScript('stepjavascript', '

  $("#Product_cid").change(function (){             
        var cid = $("#Product_cid").val();
        var path = "'.$this->createUrl('gotoController/mysubcategory').'";
        $.ajax({  
        type: "POST",      
        url: path, //url to be called
        data: { cid: cid }, //data to be send
        success: function( response ) {
            $("#sub-category-wrapper").html(response);
         }
        })

     });
     
', CClientScript::POS_END);
?>