EsiListener.php

<?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier <fabien@symfony.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */
namespace Symfony\Component\HttpKernel\EventListener;

use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\HttpKernelInterface;
use Symfony\Component\HttpKernel\Event\FilterResponseEvent;
use Symfony\Component\HttpKernel\KernelEvents;
use Symfony\Component\HttpKernel\HttpCache\Esi;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

/**
 * EsiListener adds a Surrogate-Control HTTP header when the Response needs to be parsed for ESI.
 *
 * @author Fabien Potencier <fabien@symfony.com>
 */
class EsiListener implements EventSubscriberInterface {
  private $esi;

  /**
   * Constructor.
   *
   * @param Esi $esi An ESI instance
   */
  public function __construct(Esi $esi = null) {
    $this->esi = $esi;
  }

  /**
   * Filters the Response.
   *
   * @param FilterResponseEvent $event A FilterResponseEvent instance
   */
  public function onKernelResponse(FilterResponseEvent $event) {
    if (HttpKernelInterface::MASTER_REQUEST !== $event
      ->getRequestType() || null === $this->esi) {
      return;
    }
    $this->esi
      ->addSurrogateControl($event
      ->getResponse());
  }
  public static function getSubscribedEvents() {
    return array(
      KernelEvents::RESPONSE => 'onKernelResponse',
    );
  }

}