ServiceLayer with event dispatching

composer.json

{
    "name": "starfleet/voyager",
    "authors": [
        {
            "name": "Guillem CANAL",
            "email": "nobody@nowhere.tld"
        }
    ],
    "require": {
        "symfony/event-dispatcher": "~2.4"
    }
}

voyager.php

<?php

use Symfony\Component\EventDispatcher\Event as EventBase;
use Symfony\Component\EventDispatcher\EventDispatcher;
use Symfony\Component\EventDispatcher\EventDispatcherInterface;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

require 'vendor/autoload.php';

// Courtesy of GuzzlePHP
// @see https://github.com/guzzle/guzzle/blob/master/src/Guzzle/Common/AbstractHasDispatcher.php
// @licence https://github.com/guzzle/guzzle/blob/master/LICENSE
trait Dispatcher
{
    protected $eventDispatcher;

    public static function getAllEvents()
    {
        return array();
    }

    public function setEventDispatcher(EventDispatcherInterface $eventDispatcher)
    {
        $this->eventDispatcher = $eventDispatcher;

        return $this;
    }

    public function getEventDispatcher()
    {
        if (!$this->eventDispatcher) {
            $this->eventDispatcher = new EventDispatcher();
        }

        return $this->eventDispatcher;
    }

    public function dispatch($eventName, array $context = array())
    {
        return $this->getEventDispatcher()->dispatch($eventName, new Event($context));
    }

    public function addSubscriber(EventSubscriberInterface $subscriber)
    {
        $this->getEventDispatcher()->addSubscriber($subscriber);

        return $this;
    }
}

class Event extends EventBase
{
	protected $context;

	public function __construct(array $context)
	{
		$this->context = $context;
	}
	public function __get($name)
	{
		if (!isset($this->context[$name])) {
			throw new Exception(sprintf('The "%s" context does not exist'));
		}
		return $this->context[$name];
	}
}

class NarratorSubscriber implements EventSubscriberInterface
{

	public static function getSubscribedEvents()
	{
		return array(
			'episode.before_create' 	=> array('onBeforeCreate', -255),
			'episode.after_create' 		=> array('onAfterCreate', 255),
			'episode.create'			=> array('onCreate', 0)
		);
	}

	public function onBeforeCreate(Event $event)
	{

		printf("[START]: StarDate %s...\n", self::generateStarDate());
	}

	public function onAfterCreate(Event $event)
	{
		printf("[END]: The end... Or is it?\n");
	}

	public function onCreate(Event $event)
	{
		$episode = $event->episode;
		printf("[TITLE]: %s\n", $episode->getTitle());
	}

	/**
	 * Generate StarDate
	 * @see http://trekguide.com/Stardates.htm
	 * @return float
	 */
	public static function generateStarDate()
	{
		
		$period = iterator_to_array(new DatePeriod(new DateTime('2371-01-01'), new DateInterval('P1M'), new DateTime('2378-04-06')));
		$index = rand(0, count($period) -1);

		$starDateZero = new DateTime('July 5, 2318 12:00:00');
		$seconds = ($period[$index]->getTimestamp() - $starDateZero->getTimestamp());

		$findStarYear = $seconds / 34367.0564;
		$findStarYear = floor($findStarYear * 100);
		$findStarYear = $findStarYear / 100;

		return $findStarYear;
	}
}

class AssimilationNotification extends Exception {}
class BorgCubeSubscriber implements EventSubscriberInterface
{
	public static function getSubscribedEvents()
	{
		return array(
			'episode.create' 	=> array('onCreate', 255)
		);
	}

	public function onCreate(Event $event)
	{
		// The odds of a Bord Ship encounter in this sector are about 50%
		if (rand(0, 1) % 2) {
			throw new AssimilationNotification("[Borg Cube]: We are the borgs... Prepare to be assimilated... Resistance is futile", 0);
		}
	}
	
}

class USSVoyagerCrewMembersSubscriber implements EventSubscriberInterface
{
	public static function getSubscribedEvents()
	{
		return array(
			'episode.create' 		=> array('randomDialog', 0),
			'episode.exception' 	=> array('onException', 255)
		);
	}

	public function randomDialog(Event $event)
	{
		switch(rand(1, 3)) {
			case 1 : $message = '[Janeway]: At ease, Ensign, before you sprain something'; break;
			case 2 : $message = '[Neelix]: Mr. Vulcan, nice to meet you!'; break; 
			case 3 : $message = '[Doctor]: Please state the nature of the medical emergency'; break; 
		}

		print $message . PHP_EOL;
	}

	public function onException(Event $event)
	{
		$exception = $event->exception;

		if ($exception instanceof AssimilationNotification) {
			print $exception->getMessage() . PHP_EOL;
			print "[Janeway]: Stand-by red alert... Lieutenant Paris, " . 
			"evasive maneuver! Commander Tuvok, modulate the shield frequency to escape their tractor beam" . PHP_EOL;
			$event->stopPropagation();
		}
	}
}

class Episode
{
	protected $id;
	protected $title;

	public function setTitle($title)
	{
		$this->title = $title;
	}
	public function getTitle()
	{
		return $this->title;
	}
	public function setId($id)
	{
		$this->id = $id;
	}
	public function getId()
	{
		return $this->id;
	}

}

class EpisodeService
{
	use Dispatcher;

	public function create($name)
	{
		$this->dispatch('episode.before_create');

		$episode = new Episode();
		$episode->setTitle($name);

		try {
			$episode->setId(1);
			$this->dispatch('episode.create', array('episode' => $episode));
		} catch (Exception $e) {
			$this->dispatch('episode.exception', array('exception' => $e));
			return NULL;
		}

		$this->dispatch('episode.after_create', array('episode' => $episode));

		return $episode;
	}
}


$userService = new EpisodeService();
$userService->addSubscriber(new NarratorSubscriber());
// Uncomment the line below to send borg cube in the vicinity of Voyager
// $userService->addSubscriber(new BorgCubeSubscriber());
$userService->addSubscriber(new USSVoyagerCrewMembersSubscriber());
$userService->create('My Episode');