Question mark in redirect url - Google Access Token

Google via its API, to manage the Access Token or Authorization code for updating the token itself, redirects to a url with an intermediate code via composition:

Code:

?code=a/Lor3mIpsumD0l0r-FUCZBl4hDas47Yhd0l39hFnSITbn_GmmDh3w

How to set the Route.php file to read the contents of the variable “code”?

PHP Code:

$routes->get('callback/(:any)', .......); 


doesn't work, returns 404.

Any suggestions?