Strange behavior when overriding private methods

Question

Consider the following piece of code:

class foo {
    private function m() {
        echo \'foo->m() \';
    }
    public function call() {
        $this-         


        

Answer 1

A private method is not overridable, as a private method is not visible even to its subclasses. Defining a method as protected means it is not visible outside of the class itself or its subclasses.

If you have a method that you want to use from your parent class but want children to able to modify its behaviour, and don't want this method available externally, use protected. If you want functionality in your parent class that cannot be modified in any way by subclasses, define the method as private.

EDIT: to clarify further, if you have two methods with the same name in a parent and subclass, and these methods are defined as private, essentially the subclass method has absolutely no relation to the parent method. As stated, a private method is COMPLETELY INVISIBLE to the subclass.

Consider this:

class foo {
    private function m() {
        echo 'foo->m() ';
    }
    private function z() { echo "foo->z();"; }

    public function call() {
        $this->m();
    }
}

class bar extends foo {
    private function m() {
        echo 'bar->m() ';
    }
    public function callbar() {
        $this->m();
    }
    public function callz()
    {
       $this->z();
    }
}

Calling $bar->callz(); is going to produce an ERROR, because z does not exist in the subclass at all, not even as an inherited method.