Question

I was just wondering if the next situation could be possible or not, I’ve read the PHP Manual documentation, but I would like another perspective because it’s not so clear for me.

So I have for example one class:

class SomeClass {
    public function someFunction() {
        ...
    }
}

And an extension of it:

class Extension extends SomeClass {
    public function someOtherFunction() {
        ...
    }
}

My question is, could I be able to use the public functions inside the classes on both ways, the main class’s function inside the extended function and the other way around?

And would I be doing that how?

Answer 1

You can use the public and protectedfunctions of your parent in the extended (child) class:

class Extension extends SomeClass
{
    public function someOtherFunction() {
        $foo = $this->someFunction(); // from parent class
        return $foo;
    }
}

When class “Extension” is created, its basically a copy of “SomeClass” which you can modify in the way as you can add new functions or overwrite those of the parent class.

The parent does not know about the Extension (it can be extended multiple times, eg “JSONRequest extends Request”, “XMLRequest extends Request”). Calling extended functions from within the parent makes no sense, since the parent class can never know which childs function it should call in such a situation. This type of Inheritance is one of the basic concepts of OOP and clear interfaces.

In other words, no it will never work the other way round. And it should not.