class inherits and overloads the function, how to invoke the function of the pre-overloaded parent class with the subclass object

After the class inherits and overloads the function, how to invoke the function of the pre-overloaded parent class with the child class object
Hello everyone:
I beginner PHP, see the Inheritance and overloading part, ask a question:
Suppose class A {function My_func (...);}
Class B extends A {function My_func (...)}
The above 2 classes A and B, b inherits A, B also overloads the My_func function in a
Now build the B object $obj _b = new B ();
Suppose I want to refer to the My_func function in a with a B object,
How do I write it?

------Solution--------------------
It seems that this is called rewriting, PHP does not seem to support method overloading

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