dependent dropdown box with Yii - php

Question

i have a countries, states, cities tables , and I need 3 dropdown menus
wherein, if i select a country like e.g United States, the states dropdown menu will automatically show only the states that are under United States, and next, if I select a State like e.g California, the Cities drop down menu will only show off the Cities under California
am currently having problem implementing this in yii. I have this _form file
where these 3 dropdown should be included. I have a partial code, but I can't figure out how to make this work out
this is from the Controller
public function actionDynamicstates()
{
$sql = "SELECT StateName FROM gg_t_worldareasstates ".
"WHERE CountryID = :countryid";
$command = Yii::app()->createCommand($sql);
$command->bindValue(':countryid', $_POST['CountryID'], PDO::PARAM_INT);
$data = $command->execute();
$data = CHtml::listData($data,'StateID','StateName');
foreach($data as $value=>$name)
{
echo CHtml::tag('option',
array('value'=>$value),CHtml::encode($name),true);
}
}
this is from the _form view file
<div class="row">
<?php
$country = new CDbCriteria;
$country->order = 'CountryName ASC';
echo $form->dropDownList($model, 'CountryID',
CHtml::listData
(
Worldareascountries::model()->findAll($country),
'CountryID',
array
(
'ajax' => array
(
'type' => 'POST',
'url' => CController::createUrl('wsmembersdetails/dynamicstates'),
'update' => '#StateID',
)
)
)
);
echo $form->dropDownList('StateID','', array());
?>
</div>
I changed that those codes above into this one
<div class="row">
<?php echo $form->labelEx($model,'Country'); ?>
<?php
$country = new CDbCriteria;
$country->order = 'CountryName ASC';
?>
<?php
echo $form->dropDownList($model,'CountryID',CHtml::listData(Worldareascountries::model()->findAll($country),'CountryID','CountryName'),
array(
'ajax' => array(
'type' => 'POST',
'url' => CController::createUrl('wsmembersdetails/dynamicstates'),
'update' => "#StateID"
)
)
);
?>
<?php echo $form->error($model,'CountryID'); ?>
</div>
<div class="row">
<?php echo $form->labelEx($model,'State'); ?>
<?php
$state = new CDbCriteria;
$state->order = 'StateName ASC';
?>
<?php
echo $form->dropDownList($model,'StateID',CHtml::listData(Worldareasstates::model()->findAll($state),'StateID','StateName'),
array(
'ajax' => array(
'type' => 'POST',
'url' => CController::createUrl('wsmembersdetails/dynamiccities'),
'update' => '#CityID'
)
)
);
?>
<?php echo $form->error($model,'StateID'); ?>
</div>
<div class="row">
<?php echo $form->labelEx($model,'CityID'); ?>
<?php echo $form->dropDownList($model,'CityID','',array());?>
<?php echo $form->error($model,'CityID'); ?>

Answer 1

change this line
$data = $command->execute();
to
$data = $command->query();

Answer 2

this problem was solved, it's on the yii wiki docs