PHP 5.4 - 'closure $this support'

Question

I see that the new planned features for PHP 5.4 are: traits, array dereferencing, a JsonSerializable interface and something referred to as \'closure $this support

Answer 1

One thing that Gordon missed is re-binding of $this. While what he described is the default behaviour, it is possible to re-bind it.

Example

class A {
    public $foo = 'foo';
    private $bar = 'bar';

    public function getClosure() {
        return function ($prop) {
            return $this->$prop;
        };
    }
}

class B {
    public $foo = 'baz';
    private $bar = 'bazinga';
}

$a = new A();
$f = $a->getClosure();
var_dump($f('foo')); // prints foo
var_dump($f('bar')); // works! prints bar

$b = new B();
$f2 = $f->bindTo($b);
var_dump($f2('foo')); // prints baz
var_dump($f2('bar')); // error

$f3 = $f->bindTo($b, $b);
var_dump($f3('bar')); // works! prints bazinga

The closures bindTo instance method (alternatively use the static Closure::bind) will return a new closure with $this re-bound to the value given. The scope is set by passing the second argument, this will determine visibility of private and protected members, when accessed from within the closure.

• PHP: Closure
• Blog post: Closure Object Binding in PHP 5.4