yii set selected dropdownlist from other dropdownlist - drop-down-menu

Question

i have 4 dropdownlist, 1 dropdownlist as master to control 3 dropdownlist other, this my sample code for master dropdownlist.
<div class="row">
<?php echo $form->labelEx($truck,'Truck'); ?>
<?php echo CHtml::dropDownList('idt',$truck->idt,CHtml::listData(Truck::model()->findAll(),'idt','number'),
array(
'value'=>'1',
'ajax' => array(
'type'=>'POST',
'url'=>CController::createUrl('FindTruck'),
'data'=>array('idt'=>'js:this.value'),
'dataType'=>'html',
))); ?>
</div>
<div class="row">
<?php echo $form->labelEx($employee,'Driver'); ?>
<?php echo CHtml::dropDownList('driver','$variable',CHtml::listData(Employe::model()->findAll(),'ide','name')); ?>
</div>
This My js setDriver
function setDriver(name,value){
document.getElementById(name).value = value
}
and this my controller
public function actionFindTruck() {
echo "<script>setDriver('driver',3);</script>"; // test satatic data
}
the question what code must i write on controller (ActionFindTruck) to change value of $variable above, so if i change Truck, the Driver will be change selected.
Thanks for help.

Answer 1

This is the way I did it, you should be able to change the values to your environment:
public function actionUpdateDropdown()
{
// ajax function to retrieve categories by country:
$lang_id = (!empty($_POST['feature']['language_id'])) ? $_POST['feature']['language_id'] : DEFAULT_LANG_ID;
$data = category::model()->findAll('language_id=:parent_id',
array(':parent_id'=>(int) $lang_id));
$data = CHtml::listData($data,'id','name');
if (!empty($data)) { echo '<option value="">Select Category...</option>'; }
foreach($data as $value=>$name) {
echo CHtml::tag('option',
array('value'=>$value),CHtml::encode($name),true);
}
}

Answer 2

There is a nice discussion of creating dependent drop downs at this URL:
Creating a dependent dropdown