protected function visit_headers(RequestInterface $request, $value, $flags) { if (!is_array($value)) { throw new InvalidArgumentException('headers value must be an array'); } if ($flags & self::OPTIONS_AS_DEFAULTS) { foreach ($value as $key => $header) { if (!$request->hasHeader($key)) { $request->setHeader($key, $header); } } } else { $request->addHeaders($value); } }