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Date: Thu, 10 Jun 2004 09:11:54 +0200 (CEST)
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To: Sara Golemon <pollita@php.net>
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Subject: Re: [PHP-DEV] Re: Confusing pointers in PHP 4 and 5
From: derick@php.net (Derick Rethans)

Hey,

put this in thedocs somewhere?

regards,
Derick


On Wed, 9 Jun 2004, Sara Golemon wrote:

> That's true.  What I left out of my explanation (in order to keep it simple)
> is that when you "copy" a variable, a new label is created to point to the
> same zval, and the zval's refcount is incrmented but the is_ref flag is
> *not* set (I referred to this offhand as non-reference manner of multiple
> labels referring to the same value).  Then when one of the referring labels
> says "I want to change my `copy` of the data."  It notices that someone else
> is also referring to this value (in a non-reference manner) and "separates"
> the zval:  This amounts to making a true copy of the zval (with a refcount
> of 1, and an is_ref of 0) and decrements the refcount of the original zval
> (since one fewer label is referring to it).  This is the process known as
> "copy on change".
>
> $foo = 1;
>
> /* $foo (label) ------>   1(value) (is_ref:0  refcount:1) */
>
> $bar = $foo;
>
> /*  $foo (label) ------->  1(value) */
> /*  $bar (label) ---/        (is_ref:0 refcount:2) */
>
> $foo = 2;
>
> /* $bar (label) ------->  1(value) (is_ref:0  refcount:1) */
> /* $foo (label) ------->  2(value) (is_ref:0  refcount:1) */
>
> -Sara
>
> Ya just had to make it complicated didn't you.
>
>