I’m sorry to misread your question.
You don’t need to specify the query strings.
So you should change the registering Callback URL like below.
- https://www.mydomain.com/index.php?dispatch=auth.process&hauth_done=Twitter
- → https://www.mydomain.com/index.php
You can specify the query strings in “POST oauth/request_token” endpoint instead.
https://developer.twitter.com/en/docs/basics/authentication/api-reference/request_token
Thanks.