Onsubmit call function in yii - yii

Question

I want to call function when submit form in yii. In my form I enabled validateOnSubmit.
when in call function form Onsubmit mean it will call function in twice.
My Coding,
<?php
$form = $this->beginWidget('CActiveForm', array(
'id' => 'question-form',
// Please note: When you enable ajax validation, make sure the corresponding
// controller action is handling ajax validation correctly.
// There is a call to performAjaxValidation() commented in generated controller code.
// See class documentation of CActiveForm for details on this.
'enableAjaxValidation' => true,
'enableClientValidation' => false,
'clientOptions' => array(
'validateOnSubmit' => true,
'validateOnChange' => false,
),
'htmlOptions' => array('onsubmit' => 'return checkmultiple()',),
));
?>
<div class="form-group">
<?php echo $form->labelEx($model, 'question_title'); ?>
<?php echo $form->textField($model, 'question_title', array('size' => 50, 'maxlength' => 250, 'class' => 'form-control')); ?>
<?php echo $form->error($model, 'question_title'); ?>
</div>
<?php if ($tileAssigned == Yii::app()->const->FLAG_ZERO) { ?>
<div class="form-group">
<?php echo $form->labelEx($model, 'type', array('label' => 'Is Multiple Choice')); ?>
<?php echo $form->radioButtonList($model, 'type', $yesnoList, array('separator' => '', 'onchange' => 'questionTypeChange(this.value);', 'class' => '')); ?>
<?php echo $form->error($model, 'type'); ?>
</div>
I am calling function checkmultiple mean it will call twice.
function checkmultiple()
{
}