Building a web application can be as simple as adding a few methods to your controller:

class PostsController extends Controller
{
    /** 
     * Route /posts/:id
     *
     * @param Request $request
     * @return View
     */
    public function showAction($request)
    {
        $id = $request->getParam('id');
        $post = $this->getModel('Post')->find($id); 
        if (! isset($post->id)) {
            return $request->redirect('/page-not-found');
        }
        
        $view = $this->initView();
        $view->post = $post;
        $view->user = $request->getSession()->user
        
        return $view;
    }
    
    /** 
     * Route /posts/create
     *
     * @param Request $request
     * @return View|null
     */
    public function createAction($request)
    {
        $view = $this->initView();
        if ('POST' !== $request->getMethod()) {
            return $view;
        }
        
        try {
            $post = new Post(array(
                'title' => $request->getPost('title'), 
                'text'  => $request->getPost('text')
            ));            
        } catch (ValidationException $e) {
            $view->error = $e->getMessage();
            return $view;
        }

        $id = $this->getModel('Post')->save($post);
        return $request->redirect('/posts/' . $id);
    }
}

Entity Class

You can add validation to your entity class to ensure that the values sent by the user are correct before saving them to the database:

class Post extends Entity
{
    protected $id;
    protected $title;
    protected $text;
    
    // sanitize and validate title (optional) 
    public function setTitle($value)
    {
        $value = htmlspecialchars(trim($value), ENT_QUOTES);
        if (empty($value) || strlen($value) < 3) {
            throw new ValidationException('Invalid title');
        }
        $this->title = $title;
    }
    
    // sanitize text (optional) 
    public function setText($value)
    {
        $this->text = htmlspecialchars(strip_tags($value), ENT_QUOTES);
    }
}

Routes

Apify provides a slimmed down version of the Zend Framework router:

$routes[] = new Route('/posts/:id', 
    array(
        'controller' => 'posts',
        'action'     => 'show'
    ),
    array(
        'id'         => '\d+'
    )
);
$routes[] = new Route('/posts/create', 
    array(
        'controller' => 'posts', 
        'action'     => 'create'
    )
);

HTTP Request

GET /posts/1

Incoming requests are dispatched to the controller "Posts" and action "show".