Edit report at http://bugs.php.net/bug.php?id=51409&edit=1
ID: 51409
Updated by: ras...@php.net
Reported by: sramage at nucleuslabs dot com
Summary: foreach structure pass by reference scope issue
Status: Bogus
Type: Bug
Package: Arrays related
Operating System: FREEBSD 8.0
PHP Version: 5.2.13
New Comment:
Ah, your bug title is a bit misleading then. How is this any different
from:
$foo = array(1,2,3);
$ref = &$foo[2];
$bar = $foo;
$ref = 4;
print_r($bar);
No classes or loops required. And yes, the reference to the array
element
survives the copy there.
Previous Comments:
------------------------------------------------------------------------
[2010-03-27 01:03:50] sramage at nucleuslabs dot com
Everything you wrote was perfectly correct and I agree completely with
it but that is not the problem.
The problem is that a member of a class is being modified from outside
the class without directly referencing it.
The array $bananas was *copied* to the property $monkey->bananas before
the reference was modified.
$monkey->bananas appears to be the same array in memory as $bananas
(which is how PHP is designed to save on memory usage) at the point
which $bananas gets changed I would expect $monkey->bananas and $bananas
to diverge but they don't.
This is a very minor issue since it would be bad programming practice to
leave a pass by reference variable floating around without using
unset().
------------------------------------------------------------------------
[2010-03-26 22:36:25] ras...@php.net
This makes perfect sense. After your first foreach loop, $banana is a
reference
to the last element in your $bananas array. Anything you do to that
$banana
variable is going to affect that last element. So, in your coconut
foreach, you
are now asking PHP to assign the first element of the coconut array to
the last
element of your bananas array which is exactly the output you are
getting. No
bug here.
------------------------------------------------------------------------
[2010-03-26 22:31:41] sramage at nucleuslabs dot com
Description:
------------
When an ampersand operator is used in a foreach language construct The
pass by reference variable causes *copies* of the parent array used in
the foreach loop to be modified in any future use of the initial pass by
reference variable.
This is very hard to explain clearly but see the test script below for
clarification it is a very simple test script.'
Similar bugs like this have been reported and documentation outlines a
simple workaround that does work and solves my problem.
but I figured I would report this problem as *copies* of the array are
affected and it seems kind of strange.
Test script:
---------------
class Monkey{
public $bananas=array();
public function AddBananas($bananas){
$this->bananas=$bananas;
}}
$bananas=array();
$bananas['banana1']=array('color'=>'yellow','size'=>'big');
$bananas['banana2']=array('color'=>'green','size'=>'small');
$coconuts=array();
$coconuts['coconut1']['size']='tiny';
$coconuts['coconut2']['size']="I'm a";
$monkey=new Monkey();
foreach($bananas as $key=>&$banana){
$banana['id']=$key+1;
}
$monkey->AddBananas($bananas);
foreach($coconuts as $banana){
$banana['type']="coconut!";
}
print_r($monkey->bananas);
Expected result:
----------------
Array
(
[banana1] => Array
(
[color] => yellow
[size] => big
[id] => 1
)
[banana2] => Array
(
[color] => green
[size] => small
[id] => 2
)
)
Actual result:
--------------
Array
(
[banana1] => Array
(
[color] => yellow
[size] => big
[id] => 1
)
[banana2] => Array
(
[size] => I'm a
[type] => coconut!
)
)
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/bug.php?id=51409&edit=1
