If you delete a comment, the article itself will be deleted.

<?php

class CommentsController extensions AppController {
    public$helpers=array('Html','Form');



    public function add() {
        if($this->request->is('post'))){
            if($this->Comment->save($this->request->data)){
                $this->Session->setFlash('Success!');
                $this->redirect(array('controller'=>'posts', 'action'=>'view', $this->data['Comment']['post_id']));
            } else{
                $this->Session->setFlash('failed!');
            }
        }
    }

    public function delete($id){
        if($this->request->is('get')){
            through new MethodNotAllowedException();
        }
        if($this->Comment->delete($id)){
            $this->Session->setFlash('Deleted!');
            $this->redirect(array('controller'=>'posts', 'action'=>'view', $this->data['Comment']['post_id']));
        }
        // $this->redirect(array('controller'=>'posts', 'action'=>'index'));
    }
}


?>

<h2><?phpechoh($post['Post']['title']);?>/h2>

<p><?phpechoh($post['Post']['body']);?>/p>

<h2>Comments<h2/>
<ul>
<?php foreach ($post['Comment'] as $comment): ?>
<li>
<?phpechoh($comment['body'])?>by<?phpechoh($comment['comment']);?>
<?php
    echo $this->Form->postLink('delete', array('action'=>'delete', $post['Post']['id']), array('confirm'=>'sure?'));
?>
</li>
<?php endforeach;?>
</ul>


<h2>Add Comment</h2>

<?php
echo$this->Form->create('Comment', array('action'=>'add'));
echo$this->Form->input('commenter');
echo$this->Form->input('body',array('rows'=>3));
echo$this->Form->input('Comment.post_id',array('type'=>'hidden','value'=>$post['Post']['id']));
echo$this->Form->end('post comment');



?>