ForkNetwork / guzzle3

        $response->setHeader('Via', sprintf('%s GuzzleCache/%s', $request->getProtocolVersion(), Version::VERSION));

        $lookup = ($params['cache.lookup'] === true ? 'HIT' : 'MISS') . ' from GuzzleCache';

        if ($header = $response->getHeader('X-Cache-Lookup')) {

            // Don't add duplicates

            $values = $header->toArray();

            $values[] = $lookup;

            $response->setHeader('X-Cache-Lookup', array_unique($values));

        } else {

            $response->setHeader('X-Cache-Lookup', $lookup);

        }

        if ($params['cache.hit'] === true) {

            $xcache = 'HIT from GuzzleCache';

            $xcache = 'MISS from GuzzleCache';

        }

        if ($header = $response->getHeader('X-Cache')) {

            // Don't add duplicates

            $values = $header->toArray();

            $values[] = $xcache;

            $response->setHeader('X-Cache', array_unique($values));

        } else {

            $response->setHeader('X-Cache', $xcache);

        }

        if ($response->isFresh() === false) {

            $response->addHeader('Warning', sprintf('110 GuzzleCache/%s "Response is stale"', Version::VERSION));