Tutorial missing some understanding

I have follow the tutorial here https://docs.phalcon.io/en/latest/reference/tutorial.html#creating-a-controller

Here is the Signup controller (app/controllers/SignupController.php):

<?php

class SignupController extends \Phalcon\Mvc\Controller
{

public function indexAction()
{

}

}

The empty index action gives the clean pass to a view with the form definition (app/views/signup/index.phtml):

I did not see the code that pass from controller to view: app/views/signup/index.phtml