Dropdownlist not working

in view



        <link rel="stylesheet" type="text/css" href="<?php echo Yii::app()->theme->baseUrl; ?>/css/styles.css" />




            echo CHtml::dropDownList('country_id','', array(1=>'USA',2=>'France',3=>'Japan'),


'ajax' => array(

'type'=>'POST', //request type

'url'=>CController::createUrl('currentController/dynamiccities'), //url to call.

//Style: CController::createUrl('currentController/methodToCall')

'update'=>'#city_id', //selector to update

//'data'=>'js:javascript statement' 

//leave out the data key to pass all form values through



//empty since it will be filled by the other dropdown

echo CHtml::dropDownList('city_id','', array());




In controller


 class currentController extends CController


       public function actionDynamiccities()



                  array(':parent_id'=>(int) $_POST['country_id']));



    foreach($data as $value=>$name)


        echo CHtml::tag('option',






it is not showing the data in another dropdownlist why.