+ if (isset($options['on_headers'])) {
+ if (!is_callable($options['on_headers'])) {
+ throw new \InvalidArgumentException('on_headers must be callable');
+ }
+ try {
+ $options['on_headers']($response);
+ } catch (\Exception $e) {
+ $msg = 'An error was encountered during the on_headers event';
+ $response = new RequestException($msg, $request, $response, $e);
+ }
+ }
+