How to modify laravel 5.6 login behaviour? How to add more fields for logging along with email and password?

Laravel has 2 fields in its auth to help user login i.e email and password. I have added another field(hidden field) in login blade to pass a random number along with password and email. In my eloquentuserprovider.php i am grabbing $credentials[‘password’] and $credentials[‘email’] like this but when i write $credentials[‘hidden’] i get an error saying ‘undifined index hidden’.

So my question is how should i add other fields along with email and password to validate the user I am writing all my validation logic in eloquentuserprovider.php

via Chebli Mohamed