/**
  * check_authentication mode request
  **/
 private function checkAuthentication(array $parameters, $manager = null)
 {
     $credentials = new OpenIdCredentials(HttpUrl::create()->parse($parameters['openid.identity']), $this->httpClient);
     $request = HttpRequest::create()->setMethod(HttpMethod::post())->setUrl($credentials->getServer());
     if (isset($parameters['openid.invalidate_handle']) && $manager) {
         $request->setPostVar('openid.invalidate_handle', $parameters['openid.invalidate_handle']);
     }
     foreach (explode(',', $parameters['openid.signed']) as $key) {
         $key = 'openid.' . $key;
         $request->setPostVar($key, $parameters[$key]);
     }
     $request->setPostVar('openid.mode', 'check_authentication')->setPostVar('openid.assoc_handle', $parameters['openid.assoc_handle'])->setPostVar('openid.sig', $parameters['openid.sig'])->setPostVar('openid.signed', $parameters['openid.signed']);
     $response = $this->httpClient->send($request);
     if ($response->getStatus()->getId() != HttpStatus::CODE_200) {
         throw new OpenIdException('bad response code from server');
     }
     $result = $this->parseKeyValueFormat($response->getBody());
     if (!isset($result['is_valid']) || $result['is_valid'] !== 'true' && $result['is_valid'] !== 'false') {
         throw new OpenIdException('strange response given');
     }
     if ($result['is_valid'] === 'true') {
         if (isset($result['invalidate_handle']) && $manager) {
             $manager->purgeByHandle($result['invalidate_handle']);
         }
         return true;
     } elseif ($result['is_valid'] === 'false') {
         return false;
     }
     Assert::isUnreachable();
 }