Description:
------------
This is in reference to circular references, as outlined in this bug:

https://bugs.php.net/bug.php?id=33595

The "solution" in PHP 5.3 is the garbage collector, which seems to work well. 
But it's lazy, meaning it only frees memory when it has to. On a complex web 
application I came across a situation where the garbage collector didn't free 
memory like it should have. Eventually the script ran out of memory. Granted it 
got a lot farther than 5.2 did.

The most common occurrence (only?) of a circular reference is a parent and child 
relationship with objects. The unset() function is useless because a reference 
is held, so __destruct is never ran.

I propose an additional more aggressive function called release(). It would 
function just like unset(), but would additionally call a __release() method 
within the object allowing for cleanup before unsetting the object.

If the __release() method doen't exist perhaps PHP could unset the properties 
itself, and call __release() on any objects that may be stored in an 
array/property.

I've added a demo of how this could work. The demo is different in that it 
requires __release(). An internal solution may not.

Test script:
---------------
gc_disable();

interface Release {
	function __release();
}

class A implements Release {
	function __construct() {
		$this->b = new B($this);
	}

	function __release() {
		unset($this->b);
	}
}

function release(Release &$obj) {
	$obj->__release();
	$obj = NULL;
}

class B {
	function __construct($parent = NULL) {
		$this->parent = $parent;
	}
}

for($i = 0; $i < 1000000; $i++) {
    $a = new A();
    release($a);
}