Question

I have the following class in PHP5.3:

class MyClass {
    public $a=1;
    public $hook;
    function setHook(){
        $t=$this;
        $this->hook=function() use($t){
            echo $t->a;
        };
   }
}

The following syntax works as expected:

$x = new MyClass();
$x->setHook();
call_user_func($x->hook);     // outputs 1;

However if I continue with this code:

$y = clone $x;
$y->a = 2;
call_user_func($y->hook);

Then it would still output 1. I understand WHY it’s happens, because i’ve assigned a local variable which got embedded into the definition of my closure and subsequently into the “hook” property.

Please suggest how to get around this problem. For a class containing property with “callable” how do I clone it and make closures properly reference current object. Perhaps I can follow a different pattern. Thanks!

Answer 1

You could simply overwrite the $hook when you clone:

public function __clone() {
    $this->setHook();
}

Not sure if your example is representative of your actual code. I hope it helps.

In PHP 5.4, you can use Closure::bindTo and $this directly in the closure:

class MyClass {
    public $a = 1;
    public $hook;

    public function setHook(){
        $this->hook=function() {
            echo $this->a;
        };
    }

    public function __clone() {
        $this->hook = $this->hook->bindTo($this);
    }
}