Saving data of dependent drop-down - Yii - php

Question

I am implementing a dependent drop-down and want to save their IDs in the table CANDIDATE.
I have a table named as CENTER which has two columns ID, NAME.
My other table is DISTRICT which has three columns ID, NAME and CENTER_ID.
By selecting the CENTER , I am populating the DISTRICT drop-down but the district_id is not being saved in the table CANDIDATE .
_form
<div class="row">
<?php echo $form->labelEx($model, 'district_id'); ?>
<?php
$dist = CHtml::listData(Center::model()->findAll(array('order' => 'id')), 'id', 'name');
echo $form->dropDownList($model, 'center_id', $dist, array(
'prompt' => '–select district–',
'ajax' => array('type' => 'POST',
'url' => CController::createUrl('candidate/districts'),
'update' => '#center_id',
)
));
?>
<?php
echo CHtml::dropDownList('center_id','', array());
?>
</div>
CandidateController
public function actionDistricts() {
$centers = District::model()->findAll('center_id =:id', array(':id' => (int) $_POST['Candidate']['center_id']));
$return = CHtml::listData($centers, 'id', 'name');
foreach ($return as $centerId => $centerName) {
echo CHtml::tag('option', array('value' => $centerId), CHtml::encode($centerName), true);
}
}

Answer 1

1) It seems like your url is not properly created:
'url' => CController::createUrl('districts')
Try:
'url' => CController::createUrl('candidate/districts')
2) The form you post:
$form->dropDownList($model, 'district_id', $dist...
It posts district_id to CandidateController/actionDistricts(), where you do following:
$centers = Center::model()->findAll('id=:id', array(':id' => (int) $_POST['Candidate']['center_id']));
I can't see any input containing center_id, moreover, firing Center::model()->findAll('id:id'..) doesn't make sense, if you search by primary key (id), do Center::model()->findByPk($id);
Anyways, back to the problem, your firebug log sais it all, it can't read center_id form $_POST variable, so to finish it up, try rewriting actionDistricts().
I can't guess what kind of relation (one district, several centers per 1?) your db has, so i wont be able to fully fix the problem here. But you should rewrite
$centers = Center::model()->findAll('id=:id', array(':id' => (int) $_POST['Candidate']['center_id']));
to something that expects $_POST['Candidate']['district_id'].

Answer 2

Replace
'url' => CController::createUrl('districts'),
By
'url' => $this::createUrl('candidate/districts'),