Exception returned from $app->modelsManager->executeQuery($phql)

Hi, I'm trying to create an API with Phalcon for the first time. I have been followed the tutorial "http://docs.phalconphp.com/en/latest/reference/tutorial-rest.html", but encoutered a problem. I've been created a new project with all the settings, and inside I got: 1) a "models" folder with "photos.php" file 2) a "index.php" with connection to my DB and function to retrieve information from "photos" table

The problem is that when I'm trying to activate the function through the browser i get an Error: "Phalcon\Mvc\Model\Exception: Model 'photos' could not be loaded in C:\wamp\www\Test\index.php on line 77".

line 77 => "$photos = $app->modelsManager->executeQuery($phql);"

What can cause this problem?

thanks in advance.