Dependant dropdownList Yii ajax

      echo $form->dropDownList($moveAssign,'department',CHtml::listData(ModelName::model()->findAll(array('condition'=>'enable=:enable','params'=>array('enable'=>'1'))),'department_id','department_title'),array('empty'=>'Select Department','ajax' => array(
      'type'=>'POST',
      'url'=>CController::createUrl('tickets/staffsList'),
      'update'=>'#staff')));


      echo $form->dropDownList($model,'staff',array(),array('id'=>'staff'));