Cannot update textfield based on dropdown list Yii - php

Question

I have 3 dependent dropdowns, and a textfield being dependent to the last dropdown. If one of the value in the last dropdown, I want the textfield value dynamically changes based on the selected value (it's from the same Database table).
This is the view of the third dropdown:
<div class="row" id="id_subkeg">
<?php echo $form->labelEx($model, 'id_subkeg'); ?>
<?php
echo $form->dropDownList($model, 'id_subkeg', array(), array(
'style' => 'width: 100%',
'ajax' => array(
'type' => 'POST',
'url' => CController::createUrl('dynamicSatuan'),
'update' => '#' . CHtml::activeId($model, 'satuan'),
//'update'=>'#seksi',
'data' => array('id_subkeg' => 'js:this.value'),
)
)
);
?>
<?php echo $form->error($model, 'id_subkeg'); ?>
</div>
This is the textfield view:
<div class="row" id="satuan">
<?php echo $form->labelEx($model, 'satuan'); ?>
<p class="hint" style="font-size: 80%">Contoh: Dokumen.</p>
<?php echo $form->textField($model, 'satuan', array('style' => 'width: 98%;', 'readonly' => FALSE)); ?>
<?php echo $form->error($model, 'satuan'); ?>
</div>
And this is the action in the controller:
public function actionDynamicSatuan() {
//$data = Subkegiatan::model()->findByPk($_POST['id_subkeg']);
$data = Subkegiatan::model()->findByPk('id_subkeg=:id_subkeg', array(':id_subkeg' => (int) $_POST['id_subkeg']));
echo $data->satuan;
}
But it's not been working for days. I don't know which part I've missed. My guess is that the dropdown is a dependent dropdown to the one above it. So I must have missed at some part.
Any help is highly appreciated.
UPDATE:
After days of searching, finally got it:
public function actionDynamicSatuan() {
$param_country = (int) $_POST['id_subkeg'];
$maxOrderNumber = Yii::app()->db->createCommand()
->select('satuan')
->from('subkegiatan')
->where('id_subkeg = ' . $param_country)
->queryScalar();
echo '<b>SATUAN: '. $maxOrderNumber.'</b>';
//echo CHtml::tag('input', array('type' => 'text', 'value' => $maxOrderNumber));
}

Answer 1

Instead of update, use success callback:
echo $form->dropDownList($model, 'id_subkeg', array(), array(
'style' => 'width: 100%',
'ajax' => array(
'type' => 'POST',
'url' => CController::createUrl('dynamicSatuan'),
'data' => array('id_subkeg' => 'js:this.value'),
'success'=> 'function(data) {
$("#your_id_here").empty();
$("#your_id_here").append(data);
}'
)
)
);