#27399 [NEW]: Object copy neither shallow nor deep
From: php dot bugs at darwin dot no-ip dot com
Operating system: Linux 2.4.18
PHP version: 4.3.4
PHP Bug Type: Scripting Engine problem
Bug description: Object copy neither shallow nor deep
Description:
------------
Copying an object doesn't appear to work as expected for either a shallow
or a deep copy.
Reproduce code:
---------------
class Dummy {}
$listA = new Dummy();
$listA->next = new Dummy();
$listA->next->previous =& $listA;
$listA->value = "one";
$listA->next->value = "two";
$listA->next->previous->value = "ONE";
echo "ListA: ";
echo "(" . $listA->value . ", " . $listA->next->value . ")
\n";
$listB = $listA;
$listB->value = "three";
$listB->next->value = "four";
$listB->next->previous->value="THREE";
echo "(modified listB)\n";
echo "ListA: ";
echo "(" . $listA->value . ", " . $listA->next->value . ")
\n";
echo "ListB: ";
echo "(" . $listB->value . ", " . $listB->next->value . ")
\n";
Expected result:
----------------
Expected output: (ie: if PHP does a deep copy)
ListA: (ONE, two)
(modified listB)
ListA: (ONE, two)
ListB: (three, four)
This should happen because $listB->next->previous is a copy of the
reference
to $listA. Modifying it should not modify ListA OR ListB.
Possible (wrong) output: (if PHP had done a shallow copy)
ListA: (ONE, two)
(modified listB)
ListA: (THREE, four)
ListB: (three, four)
This would be the case because listB's next would be a reference to
ListA's
next.
Actual result:
--------------
Actual output:
ListA: (ONE, two)
(modified listB)
ListA: (THREE, two)
ListB: (three, four)
This looks like PHP did something between a shallow and a deep copy.
while ListB->next is a copy, ListB->next->previous still points at ListA.
(!?!)
... For an added bonus, try replacing '= new' with '=& new' and it looks
like
PHP does a shallow copy. From my reading of PHP documentation, I thought
PHP would always do deep (de-referencing) copies.
--
Edit bug report at http://bugs.php.net/?id=27399&edit=1
--
Try a CVS snapshot (php4): http://bugs.php.net/fix.php?id=27399&r=trysnapshot4
Try a CVS snapshot (php5): http://bugs.php.net/fix.php?id=27399&r=trysnapshot5
Fixed in CVS: http://bugs.php.net/fix.php?id=27399&r=fixedcvs
Fixed in release: http://bugs.php.net/fix.php?id=27399&r=alreadyfixed
Need backtrace: http://bugs.php.net/fix.php?id=27399&r=needtrace
Need Reproduce Script: http://bugs.php.net/fix.php?id=27399&r=needscript
Try newer version: http://bugs.php.net/fix.php?id=27399&r=oldversion
Not developer issue: http://bugs.php.net/fix.php?id=27399&r=support
Expected behavior: http://bugs.php.net/fix.php?id=27399&r=notwrong
Not enough info: http://bugs.php.net/fix.php?id=27399&r=notenoughinfo
Submitted twice: http://bugs.php.net/fix.php?id=27399&r=submittedtwice
register_globals: http://bugs.php.net/fix.php?id=27399&r=globals
PHP 3 support discontinued: http://bugs.php.net/fix.php?id=27399&r=php3
Daylight Savings: http://bugs.php.net/fix.php?id=27399&r=dst
IIS Stability: http://bugs.php.net/fix.php?id=27399&r=isapi
Install GNU Sed: http://bugs.php.net/fix.php?id=27399&r=gnused
Floating point limitations: http://bugs.php.net/fix.php?id=27399&r=float
Thread (3 messages)
- php dot bugs at darwin dot no-ip dot com