bertrc is it the correct place inside the class B extends A ?
That totally depends on what you are trying to do and why you want to call that parent method.
FWIW, these lines don't actually do anything:
// . . .
They reference those object properties, but they neither output them nor set any value, they just "mention" them in your source code.
Suggestion: try doing something "meaningful" in your learning code, rather than having abstract things like
$operation. Think about some real-world case where you might want to extend one class with another (or look for tutorials that do that). Then I think these OOP concepts might make more sense? 🤷