Edit report at https://bugs.php.net/bug.php?id=29992&edit=1
ID: 29992
Comment by: martijn at twotribes dot com
Reported by: fletch at pobox dot com
Summary: foreach by reference corrupts the array
Status: Bogus
Type: Bug
Package: Scripting Engine problem
Operating System: linux
PHP Version: 5.0.1
Block user comment: N
Private report: N
New Comment:
Well, it is expected by the people who designed the language perhaps, but not by me. Iterating
through an array, without doing anything, shouldn't change the array. Period. If I do something
similar in another language like C++, this will never be the result.
Previous Comments:
------------------------------------------------------------------------
[2011-07-15 11:57:04] johannes@php.net
daniel,
unsetting it before might also cause a wrong result. Simple example:
<?php
function search_element($array, &$var) {
foreach ($array as &$var) {
if ($condition) {
return true;
}
}
}
$array=array(1,2,3,4,5,6);
$var = null;
search_element($array, $var);
?>
This is simplified and probably no good architecture but such designs might make sense in some
situations and breaking that adds a larger inconsistency than the current "surprising but
consistent" behavior.
martijn,
Of course there is a reference at the end, absolutely expected and consistent with the language.
------------------------------------------------------------------------
[2011-07-13 06:48:49] martijn at twotribes dot com
To elaborate of why I strongly feel this is a bug and not a 'feature':
$a = array('a', 'b', 'c', 'd');
foreach ($a as &$v) { }
var_dump($a);
One would expect that every element of $a is a string. Well it was, up until I did that
foreach-with-reference. That changed the last element into string reference:
array(4) {
[0]=>
string(1) "a"
[1]=>
string(1) "b"
[2]=>
string(1) "c"
[3]=>
&string(1) "d"
}
The PHP guys can claim that this is correct behavior all they want, but it is fundamentally wrong
from a design perspective that an array changes, without doing anything to its elements.
------------------------------------------------------------------------
[2011-07-13 06:37:58] martijn at twotribes dot com
Can someone please promote this "bogus" status to an actual bug? It completely baffles me
why something so obviously wrong, has been present in PHP for almost 7(!) years. Come on guys, fix
this!
------------------------------------------------------------------------
[2011-07-01 06:41:47] daniel at milde dot cz
I agree with Looris. This behaviour is dangerous and no one expects it.
I suggest unsetting the variable BEFORE each loop. This should cause no harm.
------------------------------------------------------------------------
[2010-11-27 14:59:24] johannes@php.net
I explained this with some pictures in my blog: http://schlueters.de/blog/archives/141-References-and-foreach.html
And no, unsetting after the loop is no option as it is inconsistent with other loops and there are
valid reasons for keeping it after the loop. Something along the lines of
foreach ($array as &$item) {
if ($item == "foo") {
break;
}
}
$item = "bar";
------------------------------------------------------------------------
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