<?php
// Don't forget to add the namespace
namespace Application\Model;

// We shouldn't forget to add these!
use Zend\EventManager\EventManager;
 
class SwagMachine
{
  // This will hold our EventManager
  private $em;

  public function getEventManager() 
  {
    // If there is no EventManager, make one!
    if (!$this->em) {
      $this->em = new EventManager(__CLASS__);
    }
 
    // Return the EventManager.
    return $this->em;
  }
 
  public function findSwag($id)
  {
    // Trigger our findSwag.begin event 
    // and push our $id variable with it.
    $response = $this->getEventManager()
                     ->trigger(
           'findSwag.begin', 
           $this,
           array(
             'id' => $id
           )
    );
  
    // Make our last response, the final 
    // ID if there is a response.
    if ($response->count() > 0)
      $id = $response->last();
 
    // ********************************
    // In the meantime important code 
    // is happening...
    // ********************************
  
    // ...And that ends up with the 
    // folowing return value:
    $returnValue = 'Original Value ('. $id. ')';
    
    // Now let's trigger our last 
    // event called findSwag.end and 
    // give the returnValue as a 
    // parameter.
    $this->getEventManager()
         ->trigger(
           'findSwag.end', 
           $this, 
           array(
             'returnValue' => $returnValue
           )
    );
 
    // Now return our value.
    return $returnValue;
  }
}

<?php

namespace Application\Controller;

use Zend\Mvc\Controller\AbstractActionController;

class IndexController extends AbstractActionController
{
  public function indexAction() 
  {
    // Get our SwagMachine
    $machine = new SwagMachine();
    
    // Let's attach our first callback, 
    // which potentially will increase 
    // the $id with 10, which would 
    // make it result in 30!
    $machine->getEventManager()
            ->attach(
        'findSwag.begin',
        function(Event $e) 
        {
          // Get the ID from our findSwag() 
          // method, and add it up with 12.
          return $e->getParam('id') + 10;
        },
        200
    );
    
    // Now attach our second callback, 
    // which potentially will increase 
    // the value of $id to 60! We give 
    // this a *higher* priority then 
    // the previous attached event 
    // trigger.
    $machine->getEventManager()
            ->attach(
        'findSwag.begin',
        function(Event $e) 
        {
        // Get the ID from our findSwag() 
        // method, and add it up with 15.
        return $e->getParam('id') + 40;
      },
      100
    );
  
    // Now create a trigger callback 
    // for the end event called findSwag.end, 
    // which has no specific priority, 
    // and will just output to the screen.
    $machine->getEventManager()
            ->attach(
        'findSwag.end',
        function(Event $e) 
        {
          echo 'We are returning: '
             . $e->getParam('returnValue');
        }
    );

    // Now after defining the triggers, 
    // simply try and find our 'Swag'.      
    echo $machine->findSwag(20);
  }
}

We are returning: Original Value (60)
Original Value (60)

Module.php:
namespace Application;

// We are going to use events, and because we use a MVC, 
// we need to use the MvcEvent.
use Zend\Mvc\MvcEvent;

class Module
{
  public function onBootstrap(MvcEvent $e)
  {
    // Get our SharedEventManager from the MvcEvent $e 
    // that we got from the method
    $sharedEvents = $e->getApplication()
                      ->getEventManager()
                      ->getSharedManager();

    // Also retrieve the ServiceManager of the 
    // application.
    $sm = $e->getApplication()->getServiceManager();

    // Let's propose a new ViewStrategy to our 
    // EventManager.
    $sharedEvents->attach(

        // We are attaching the event to this namespace 
        // only.
        __NAMESPACE__, 

        // We want to attach to this very specific 
        // event, the Dispatch event of our controller.
        MvcEvent::EVENT_DISPATCH, 

        // The callback function of the event, used when 
        // the event we attached to happens. In our 
        // callback we also want our local variable $sm 
        // to be available for use.
        function($e) use ($sm) 
        {
          // Get our alternate view strategy from the 
          // ServiceManager and attach the EventManager     
          // to the strategy.
          $strategy = $sm->get('ViewJsonStrategy');
          $view = $sm->get('ViewManager')->getView();
          $strategy->attach($view->getEventManager());
        }, 

        // We want to give this a priority, so this will 
        // get more priority.
        100
    );
}