Question

AccountController can’t extend BaseAccount and BaseController at the same time. If I make all BaseAccount or BaseController methods empty, I can have an interface, but if I implement that interface in two different places, that is, I make a contract to implement a method in two different places, I will have duplicated code. Do interfaces solve DDD with code duplication?

interface A {
    function doStuff() {
    }
}

class B implements A {
    function doStuff() {
        // a code
    }
}

class C implements A {
    function doStuff() {
        // the same code!!!
    }
}

Answer 1

Little bit confused with your last sentance, but if you want multiple inheritance then you need to do this:

AccountController extends BaseAccount, and BaseAccount extends BaseController

BaseController
  |
BaseAccount
  |
AccountController

Using this method will enable you to access all member functions of BaseAccount and BaseController from AccountController using $this.