How to find where a function is being called from in laravel?

I am Android Developer. I have started learning Laravel and I have a sample project that I am currently understanding. There are functions which are not being called from anywhere. This function has to be called on a event. On running the project the functions are called and working fine. How to know from where the functions are triggered.

I have searched the whole project for those functions and only can find one result where the function is declared, not from where its been called. I have looked in Event and Listeners folders, but can't find anything. Please help I have to complete a project which has a soon approaching deadline.

public static function generateInvoice($user,$case){
   // Do Something
}

via Chebli Mohamed