code: protected static function requestStream($url, $params)
      {
          $opts = array('http' =>
              array(
                  'method' => 'POST',
                  'header' => implode("\n", self::getHeaders()),
                  'content' => json_encode($params),
                  'timeout' => self::$requestTimeout,
                  'ignore_errors' => true,
              )
          );
  
          $context = stream_context_create($opts);
  
          return file_get_contents($url, false, $context);
      }
docs: Perform request using native PHP streams
  
  @param string $url Request URL
  @param array $params The parameters to use for the POST body
  
  @return string Response body