I'm trying to update and extend a simple "onlineconfirm" plugin mentioned here: https://moodle.org/mod/forum/discuss.php?d=354562
In "/auth/onlineconfirm/classes/" I have a file "signup_form.php" which defines a class "auth_onlineconfirm_login_signup_form". Based on what I read from https://docs.moodle.org/dev/Automatic_class_loading I gathered that this class would be autoloaded. However, even an intentional syntax error won't show up anywhere or break the flow of the signup form page. I am also reading https://docs.moodle.org/dev/Authentication_plugins but didn't find any help there for this.
How can I override the signup form class to customize its functionality? Can it be done with the class autoloading feature, i.e. can the login_signup_form class be overridden?
Using M3.5.2+