Dropdownlist not working

in view


<html>

    <head>

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

    </head>

    <body>

        <?php 

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

array(

'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());

         ?>

    </body>

</html>

In controller


<?php

 class currentController extends CController

 {

       public function actionDynamiccities()

{

    $data=Location::model()->findAll('parent_id=:parent_id', 

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

 

    $data=CHtml::listData($data,'id','name');

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

    {

        echo CHtml::tag('option',

                   array('value'=>$value),CHtml::encode($name),true);

    }

}

 }

?>



it is not showing the data in another dropdownlist why.