FriendsOfSymfony / FOSHttpCacheBundle

        $flags = array('must_revalidate', 'proxy_revalidate', 'no_transform', 'no_cache');

        $options = array('stale_if_error', 'stale_while_revalidate');

        foreach ($flags as $key) {

            $flag = str_replace('_', '-', $key);

            if (!empty($controls[$key])

                && ($overwrite || !$response->headers->hasCacheControlDirective($flag))

            ) {

                $response->headers->addCacheControlDirective($flag);

            }

        }

        foreach ($options as $key) {

            $option = str_replace('_', '-', $key);

            }

        }

        foreach ($options as $key) {

            $option = str_replace('_', '-', $key);

            if (isset($controls[$key])

                && ($overwrite || !$response->headers->hasCacheControlDirective($option))

            ) {

                $response->headers->addCacheControlDirective($option, $controls[$key]);

            }

        }

    }

    /**