Kevinrob\GuzzleCache\CacheMiddleware::getRequestWithReValidationHeader PHP Method

    protected static function getRequestWithReValidationHeader(RequestInterface $request, CacheEntry $cacheEntry)
    {
        if ($cacheEntry->getResponse()->hasHeader('Last-Modified')) {
            $request = $request->withHeader('If-Modified-Since', $cacheEntry->getResponse()->getHeader('Last-Modified'));
        }
        if ($cacheEntry->getResponse()->hasHeader('Etag')) {
            $request = $request->withHeader('If-None-Match', $cacheEntry->getResponse()->getHeader('Etag'));
        }
        return $request;
    }