ID: 48460
Updated by: jani@php.net
Reported By: ben at last dot fm
-Status: Open
+Status: Feedback
Bug Type: Scripting Engine problem
Operating System: Linux
PHP Version: 5.2.9
New Comment:
Please try using this snapshot:
http://snaps.php.net/php5.3-latest.tar.gz
For Windows:
http://windows.php.net/snapshots/
Previous Comments:
------------------------------------------------------------------------
[2009-06-03 15:26:16] ben at last dot fm
Hmm.
The bug is that you can alter the behaviour of clone (that is, force
$d-
>list to be copied-by-reference instead of copied-by-value) merely by
creating any other reference to $a->list. 'clone' is, therefore, the
only language construct (that I know of) which is capable of this, and
is NOT the same as "$b = new A; $b->list = $a->list".
There is in fact no way to tell whether a property is a reference or
not
without cloning the entire object and seeing what happens when you
change the clone's property; or by forcibly unsetting and resetting the
property.
------------------------------------------------------------------------
[2009-06-03 13:54:41] colder@php.net
This is quite expected, that's basically the same as:
$a = array(2);
$d = &$a[0];
$a_copy = $a;
$a_copy[0]++;
echo $a[0],$d; // 3 3
You can do a deep copy using the __clone hook.
OTOH I'm not sure if clone shouldn't separate the properties directly,
instead of simply assigning them.
------------------------------------------------------------------------
[2009-06-03 13:34:44] ben at last dot fm
Sorry, put this in the wrong category.
------------------------------------------------------------------------
[2009-06-03 13:32:35] ben at last dot fm
More minimal test case:
<?php
class A { var $p; }
$a = new A;
$a->list = 1;
$b = clone $a;
$link =& $a->p;
unset($link);
$c = clone $a;
$link =& $a->p;
$d = clone $a;
unset($link);
$e = clone $a;
$b->p = 2;
$c->p = 3;
$d->p = 4;
$e->p = 5;
echo "$a->p\n$b->p\n$c->p\n$d->p\n$e->p\n";
------------------------------------------------------------------------
[2009-06-03 13:29:02] ben at last dot fm
Description:
------------
If you create a reference to a property of an object, then clone
the object, the reference will become bi-directional and the property
will no longer behave like a property.
This does not happen if you create, then destroy, the reference BEFORE
cloning.
This persists even if you unset the reference AFTER cloning.
Reproduce code:
---------------
<?php
class A { var $list; }
$a = new A;
$a->list = array( 1, 1, 1, 1, 1 );
$b = clone $a;
$link =& $a->list;
unset($link);
$c = clone $a;
$link =& $a->list;
$d = clone $a;
unset($link);
$e = clone $a;
$b->list = array(2,2,2,2,2);
$c->list = array(3,3,3,3,3);
$d->list = array(4,4,4,4,4);
$e->list = array(5,5,5,5,5);
echo "$a\n$b\n$c\n$d\n$e\n";
Expected result:
----------------
{1}
{2}
{3}
{4}
{5}
Actual result:
--------------
{5}
{2}
{3}
{5}
{5}
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=48460&edit=1