Yii：保存表单模型返回404页面

I don't know what happened but at some point my form submission to save the model Students is failing. For example when I submit the form for a Student, it used to redirect to /student/33 which shows the student I just created but now it's showing 404 error. There's no error or stacktrace thrown.

How can I debug this situation? When I go to /student/22 it shows up fine. I think it must have been some change I made but can't figure out how to debug this. All I did was change the date format.

Make sure the form action is pointing to the right url. Use the action key as part of the form -

<?php $form=$this->beginWidget('CActiveForm', array(
        'id'=>'add-form',
        'action'=>$this->createUrl('site/student',array('id'=>$id)),
        'enableAjaxValidation'=>true,
        'enableClientValidation'=>false,
        'clientOptions'=>array(
          'validateOnSubmit'=>true,
          'validateOnChange'=>false,
          'validateOnType'=>true,
        ),
      )); ?>