Question

Is it possible to either

extend an extension of a class e.g.:

class a {
}
class b extends a {
}
class c extends b {
}

EDIT:

[or some other way that class c can use functions only defined in b but not in a.]

Well I just notice that my question was kinda messed up. c should be able to use all functions, so of course those of a aswell.

I’ll just accept the answer solving my non-existing problem, in case someone searches for this.

Answer 1

Since PHP 5.4 you can use traits which may be of help to you. You can define two traits, one with the functions that class a has and one containing functions that class b has, but not class a.

So:

trait TraitA {
    function a1() { }
    function a2() { }
}

trait TraitB {
    function b1() { }
    function b2() { }
}

Then you can define a class a that uses only TraitA, a class b that uses both traits, and a class c that uses only TraitB:

class a {
    use TraitA
    // contains a1 and a2
}

class b {
    use TraitA, TraitB
    // contains a1, a2, b1 and b2
}

class a {
    use TraitB
    // contains b1 and b2
}

More on traits: http://php.net/manual/en/language.oop5.traits.php
Keep in mind that you have to pay attention to your function names between different traits. You can’t have the same functionnames in both traits or you’ll get collisions.