private function addResponseHeaders(RequestInterface $request, ResponseInterface $response) { $params = $request->getConfig(); $lookup = $params['cache_lookup'] . ' from GuzzleCache'; $response->addHeader('X-Cache-Lookup', $lookup); if ($params['cache_hit'] === true) { $response->addHeader('X-Cache', 'HIT from GuzzleCache'); } elseif ($params['cache_hit'] == 'error') { $response->addHeader('X-Cache', 'HIT_ERROR from GuzzleCache'); } else { $response->addHeader('X-Cache', 'MISS from GuzzleCache'); } $freshness = Utils::getFreshness($response); // Only add a Warning header if we are returning a stale response. if ($params['cache_hit'] && $freshness !== null && $freshness <= 0) { $response->addHeader('Warning', sprintf('%d GuzzleCache/' . ClientInterface::VERSION . ' "%s"', 110, 'Response is stale')); } }