PSR-4 for dummies with practical example

Every time I come to write a new application I always forget how to use PSR-4 so here’s my practical example

Directories:

- src
- - Digital
- - - Epok
- - - - Controller
- - - - - HomePageController.php

composer.json

{
    "require": {
        "silex/silex": "~1.1"
},
    "autoload": {
        "psr-4": {
             "Digital\\Epok\\Controller\\": "src/Digital/Epok/Controller"
        }
    }
}

HomePageController.php

<?php
  namespace Digital\Epok\Controller;

  use Silex\Application;
  use Symfony\Component\HttpFoundation\Request;

  class HomePageController {
    public function homePage(Request $request, Application $application) {
      return 'Hi';
    }
  }

Hopefully this will help me remember how I should setup PSR-4 with a new project.