Edit report at https://bugs.php.net/bug.php?id=63179&edit=1
ID: 63179
User updated by: uli dot staerk at globalways dot net
Reported by: uli dot staerk at globalways dot net
Summary: foreach: Using variable reference leads to
inconsistent data
Status: Duplicate
Type: Bug
Package: Scripting Engine problem
Operating System: Linux
PHP Version: Irrelevant
Block user comment: N
Private report: N
New Comment:
Thanks for pointing this out. I think breaking the reference is not the correct
way, because an implicit unset will also have to applied to variables and will
break peoples code.
I think the correct way you should fix this, is by calling an implicit unset
for $key and $value when BEFORE foreach and should not break any code. If you
think you are breaking code, you can issue a E_WARNING if $value is a reference
being destroyed.
Can you convert this bug report into some kind of feature request? :)
Previous Comments:
------------------------------------------------------------------------
[2012-09-29 11:06:57] notzippy at gmail dot com
I agree that this behaviour should be modified to a special case, with an
automatic unset occurring at the initialization of the second loop, or at the
block closure of the first loop. If you read the recommended practises it is
highly recommended that this is done manually after closure of the foreach
loop. I would propose that this be changed to an automatic process.
------------------------------------------------------------------------
[2012-09-29 10:46:10] [email protected]
@uli: Maybe it would help you to understand the behavior if you wrote those two
foreach loops out. Your code is roughly equivalent to the following:
<?php
// first loop
$value =& $testdata[0];
$value =& $testdata[1];
// second loop
$value = $testdata[0];
$value = $testdata[1];
So after the second loop $value is a reference to $testdata[1]. You could say
that those two variables are synonyms. So when in the second loop you assign to
$value again it is still a reference to $testdata[1]. So if you change $value,
then $testdata[1] is changed too.
Personally I think that we should break the reference after the foreach loop,
simply to avoid the WTF moment here. I just wanted to explain why the current
behavior is consistent ;)
------------------------------------------------------------------------
[2012-09-29 09:38:22] uli dot staerk at globalways dot net
The manual says: "On each iteration, the value of the current element is
assigned to $value".
This is not correct if you have a look at my example. The manual claims that an
assignment happens, but the reference has some magic override here.
Either you must fix this "consistent" implementation, or you have to fix the
documentation like "it will not be correctly assigned if $value is a reference".
------------------------------------------------------------------------
[2012-09-29 02:52:29] [email protected]
dup to #50485
------------------------------------------------------------------------
[2012-09-28 21:26:52] notzippy at gmail dot com
A variable that is the target of a foreach should be intrinsically unset and
not need a manual process to do it.
------------------------------------------------------------------------
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the rest of the comments, please view the bug report online at
https://bugs.php.net/bug.php?id=63179
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