Simulate multiple inheritance in PHP - php

Question

Assuming I have 2 classes
Class A {
public function doA(){
echo "Im A";
}
}
Class B {
public function doB(){
echo "Im B";
}
}
write Class C, in order that the following code runs:
$c = new C();
$c->doA();
$c->doB();
and outputs:
>> Im A
>> Im B
This was in a test, and the conditions where:
use no static calls
you can't modify class A or class B
so I wrote:
Class C {
public function doA() {
$a = new A();
$a->doA();
}
public function doB() {
$b = new B();
$b->doB();
}
}
So apparently I was wrong as it can be "more optimized"
can someone tell me how to do it?

Answer 1

You could keep instances of A and B instead of instantiating them each time.
class C {
private $a, $b;
public __construct() {
$this->a = new A();
$this->b = new B();
}
public function doA() {
$this->a->doA();
}
public function doB() {
$this->b->doB();
}
}

Answer 2

PHP has no "native" multiple inheritance, but you can achieve something similar to it by using traits.
Trait A {
public function doA(){
echo "Im A";
}
}
Trait B {
public function doB(){
echo "Im B";
}
}
Class C {
use A, B;
}
$c = new C;
$c->doA();
$c->doB();
Note that this would require at least PHP 5.4.

Answer 3

To do it without modifying classes, the best and optimised option would be as follows.
class C {
private $a;
private $b;
public __construct() {
$this->a = new A();
$this->b = new B();
}
public function __call($method, $arguments = array()) {
if(method_exists($this->as, $method)) {
return call_user_func(array($this->a, $method));
}
}
}
The above is also future proof, so adding new methods would also follow.
While you were told not to modify classes A and B, the correct way to do this would be by having B extend A, then having C extend B, like below.
class A {
public function doA(){
echo "Im A";
}
}
class B extends A {
public function doB(){
echo "Im B";
}
}
class C extends B {
}
$c = new C();
$c->doA();
$c->doB();