public function add() {
    $post = $this->Posts->newEntity($this->request->data, ['associated' => ['Categories' => ['validate' => 'notEmpty']]]);

    if ($this->request->is('post')) {
	$newData = ['user_id' => $this->Auth->user('id')];
	// $this->request->data['user_id'] = $this->Auth->user('id');
	$post = $this->Posts->patchEntity($post, $newData);
	// $post->user_id = $this->Auth->user('id');
	// debug($post);exit;
	if ($this->Posts->save($post)) {
	    $this->Flash->success(__('Your post has been saved.'));
    	    return $this->redirect(['action' => 'index']);
	}

	$this->Flash->error(__('Unable to save your post.'));
    }
    $categories = $this->Posts->Categories->find('list');
    $this->set('post', $post);
    $this->set(compact('post', 'categories'));
}