Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:43315
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain cakephp.org designates 209.62.120.18 as permitted sender)
Message-ID: <6E2164EC-F333-4E89-8EBD-6618BA321CD6@cakephp.org>
To: PHP Development <internals@lists.php.net>
Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
Content-Transfer-Encoding: 7bit
Mime-Version: 1.0 (Apple Message framework v930.3)
Date: Wed, 11 Mar 2009 16:25:23 -0400
Subject: Questions on closures and visibility
From: nate@cakephp.org (Nate Abele)

Hi all,

Since around alpha1, I've been doing some experimenting with closures,  
most recently in the form of a filter chain implementation, and I've  
discovered that as of beta1 (as was noted in the "removal-of-$this"  
RFC) that there is no way to access private or protected members of  
any class inside a closure, regardless of where it is defined.

I realize that the question of implicit $this support for closures has  
already been discussed and decided upon temporarily (and I certainly  
have no wish to rehash it again), however, it seems logical that even  
without being bound to an object, closures should still inherit the  
scope in which they're defined.  Otherwise, this creates a confusing  
inconsistency within the language.  Consider the following:

class Exposed {

	private $_property;

	public function __construct($data = null) {
		$this->_property = $data;
	}

	public function getProtected($self, $property) {
		return $self->$property;
	}
}

$object1 = new Exposed('secret');
$object2 = new Exposed();

// successfully echos "secret"
echo $object2->getProtected($object1, '_property'));

Because of PHP's scope and visibility rules, this works even though  
$object1 and $object2 are only associated by common parentage.  While  
this may have no technical significance, since a closure is actually  
it's own class, in practical terms it puts a damper on the usefulness  
of the implementation, and is a bit of a "WTF", particularly when  
considered in context with "use", which allows closures to inherit and  
even modify variables in the declaring scope, regardless of where they  
are called.

Again, to clarify, I am not arguing for $this support to be added back  
to closures (though if a consensus could be reached before 5.3 final,  
that'd be great, too :-)).  I am simply suggesting that the current  
implementation might be improved and made more consistent (without  
designing it into a corner concerning future decisions) by allowing a  
closure defined in class X to follow the same rules as any other  
method also defined in X.

Any thoughts or feedback would be very much appreciated.  :-)

Thanks for your time and consideration,

- Nate Abele
   Lead Developer, CakePHP