CacheControlEventSubscriber.php in HTTP Cache Control 8

Namespace

Drupal\http_cache_control\EventSubscriber

File

src/EventSubscriber/CacheControlEventSubscriber.php

<?php

namespace Drupal\http_cache_control\EventSubscriber;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpKernel\KernelEvents;
use Symfony\Component\HttpKernel\Event\FilterResponseEvent;

/**
 * Subscriber for adding http cache control headers.
 */
class CacheControlEventSubscriber implements EventSubscriberInterface {

  /**
   * Set http cache control headers.
   */
  public function setHeaderCacheControl(FilterResponseEvent $event) {
    $config = \Drupal::service('config.factory')
      ->get('system.performance');
    $response = $event
      ->getResponse();
    if (!$response
      ->isCacheable()) {
      return;
    }
    $max_age = $response
      ->getMaxAge();
    switch ($response
      ->getStatusCode()) {
      case 404:
        $ttl = $config
          ->get('cache.http.404_max_age', $max_age);
        break;
      case 302:
        $ttl = $config
          ->get('cache.http.302_max_age', $max_age);
        break;
      case 301:
        $ttl = $config
          ->get('cache.http.301_max_age', $max_age);
        break;
      default:
        $ttl = $config
          ->get('cache.page.max_age');
        break;
    }

    // Allow modules that set their own max age to retain it.
    // If a response max-age is different to the page max-age
    // then this suggests the max-age has already been manipulated.
    if ($max_age != $config
      ->get('cache.page.max_age')) {
      $ttl = $max_age;
    }
    $response
      ->setSharedMaxAge($ttl);
    $response
      ->setClientTtl($config
      ->get('cache.http.max_age'));
    if ($response
      ->getStatusCode() >= 500) {
      $response
        ->setSharedMaxAge($config
        ->get('cache.http.5xx_max_age'));
    }
    elseif ($response
      ->getStatusCode() < 400) {

      // Add stale-if-error directive.
      if ($seconds = $config
        ->get('cache.http.stale_if_error')) {
        $response->headers
          ->addCacheControlDirective('stale-if-error', $seconds);
      }

      // Add stale-while-revalidate directive.
      if ($seconds = $config
        ->get('cache.http.stale_while_revalidate')) {
        $response->headers
          ->addCacheControlDirective('stale-while-revalidate', $seconds);
      }
    }
  }

  /**
   * {@inheritdoc}
   */
  public static function getSubscribedEvents() {

    // Response: set header content for security policy.
    $events[KernelEvents::RESPONSE][] = [
      'setHeaderCacheControl',
      -10,
    ];
    return $events;
  }

}

Classes

Name	Description
CacheControlEventSubscriber	Subscriber for adding http cache control headers.