Calling Static Method from Class B(which extends Class A) of Class A

Question

There was an interesting question in a practice test that I did not understand the answer to. What is the output of the following code:

<?php
class Foo {
    public $name = 'Andrew';

    public function getName() {
        echo $this->name;
    }
}

class Bar extends Foo {
    public $name = 'John';

    public function getName() {
        Foo::getName();
    }
}

$a = new Bar;
$a->getName();
?>

Initially, I thought this was produce an error because static methods can not reference $this (atleast in PHP5). I tested this myself and it actually outputs John.

I added Foo::getName(); at the end of the script and did get the error I was expecting. So, what changes when you call a static method from within a class that extends the class you're calling from?

Would anyone mind explaining in detail exactly what is going on here?

Answer 1

Foo::getName() is using an older PHP4 style of scope resolution operator to allow an overridden method to be called.

In PHP5 you would use parent::getName() instead

It's useful if you want to extend, rather than completely override the behaviour of the base class, e.g. this might make it clearer

class Bar extends Foo {
    public $name = 'John';

    public function getName() {
        echo "My name is ";
        parent::getName();
    }
}

Answer 2

If you call the static method bound to the other object, the method is executed in the context of the current object. Which allows access to the $this-object.

Better way to call the superclass-method from inside the subclass would be:

parent::getName();