No pending_update_count from Telegram Bot
I am the author of this library but I'm not too active on StackOverflow.
The reason why you don't see anything is because Telegram is sending you the update and you process it in the same request, so that print_r() you've got is what you are sending back to Telegram.
I would recommend in this situation to save the response to a file or pass in a PSR-3 compatible logger (iirc debug level will also save the original data that came in from Telegram) so that you can see what is happening.
Happy coding!