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Re: [PHP] references, circular references, oop, and garbage collection in PHP5

Posted by Curt Zirzow on 12/07/05 05:45

I'm going to jump to the code as fast as possible to explain what I
can, the key thing to remember in php5 is that the old &$var
declaration has no real meaning in objects. php5's objects exist
outside of the old oop reference. Consider:

class Object {
public $val;
function __construct($v) {
$this->val = $v;
}
}

In PHP5:

$o = new Object(2);
$b = $o;
$b->val = 3;
print $o->val; // echos 3

in PHP4 (assuming var is used instead of public)

$o = new Object(2);
$b = $o;
$b->val = 3;
print $o->val; // echos 2

This is cause objects in php5 exist all on there own, that get
referenced to a php variable.


On Tue, Dec 06, 2005 at 05:23:45PM -0500, Alan Pinstein wrote:
>
> Question #1: Is the fact that references to objects in the form
> $objRef = &$obj don't bump the refcount of $obj an intended behavior
> that can be counted on? If so, cool!
>
> So, now that we have a way to do weak references, we should be able
> to implement a reasonable memory management scheme for parent-child
> objects.
>
> Normally from the client side the interface should look something like:
>
> $parent = new Parent();
> $child = new Child();
> $parent->addChild($child);

Ok, i get to the code and well what I mentioned above explains why there is no
need to use the $o = &$object;

If I take your code and run it against one of the latest version's
of php 5.1 i will get a var_dump($child) of:

object(pChild)#2 (1) {
["parent"]=>
object(pParent)#1 (1) {
["children"]=>
array(1) {
[0]=>
object(pChild)#2 (1) {
["parent"]=>
object(pParent)#1 (1) {
["children"]=>
array(1) {
[0]=>
*RECURSION*
}
}
}
}
}
}

Which is what I see as expected results.

Curt.
--
cat .signature: No such file or directory

 

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