当'post'替换为'get'时，为什么CakePHP会添加新行？

I edit a row on the Post table or add a new row to it from edit() function in PostsController. The function looks like this:

public function edit($id = null) {
// Has any form data been POSTed?
if ($this->request->is('post')) { //Replaced 'post' by 'get' in this line

    // If the form data can be validated and saved...
    if ($this->Post->save($this->request->data)) {

        // Set a session flash message and redirect.
        $this->Session->setFlash('Updated the Post!');
        return $this->redirect('/posts');
    }
}

// If no form data, find the post to be edited
// and hand it to the view.
$this->set('post', $this->Post->findById($id));

}

I simply replaced 'post' by 'get' to see what would happen and it went on creating new rows without even taking me to the form. I still get the flash message 'Updated the Post!', but without taking any form data.

If the code in edit.ctp is required, here it is:

<?php
echo $this->Form->Create('Post');
echo $this->Form->input('id', array('type' => 'hidden','default'=>$post['Post' ['id']));
    echo $this->Form->input('title',array('default'=>$post['Post']['title']));
    echo $this->Form->input('body',array('default'=>$post['Post']['body']));
    echo $this->Form->end('Update');
    ?>

Any thoughts on why this might be happening?

Edit: Added CakePHP Version

I am using CakePHP 2.4.5

What you are doing makes no sense. Why would you want to switch the "post" by "get" here? Of course it will then generate new rows, as you effectively trigger a save on each page load (GET). Don't do that. The code you had there was just fine - IF you also took PUT into consideration. For edit forms, it is not a post, but:

if ($this->request->is('put')) {}

PS: If you want to make sure it always works for both add/edit, use

 if ($this->request->is(array('post', 'put')) {}

But NEVER replace it with "get".