#33172 [Opn]: changing array during foreach iteration

[tomas_matousek at hotmail dot com]

 ID:               33172
 User updated by:  tomas_matousek at hotmail dot com
 Reported By:      tomas_matousek at hotmail dot com
 Status:           Open
 Bug Type:         Scripting Engine problem
 Operating System: WinXP
 PHP Version:      5.0.4
 New Comment:

Well, I've swapped the expected and the actual results.
I would expect all values of the array to be modified.


Previous Comments:
------------------------------------------------------------------------

[2005-05-28 16:24:41] tomas_matousek at hotmail dot com

Description:
------------
The behavior of foreach statment with reference value is not imho right
if the array gets modified during iteration.

See the code I've pasted here. If the array is written to (either by
unset or by a write operation) during iteration, the effect of & is
canceled, i.e. the values are not modified since the write operation.

This seems to me as bug because it is inconsistent with the
"definition" of foreach which should say that

foreach($a as $k => $v) {}

is (more or less) equivalent to 

$copy_of_a = $a;
while(next($copy_of_a))
{
  $k = key($copy_of_a);
  $v = $copy_of_a[$k];
}

With the &, one can deduce the following "definition":

foreach($a as $k =>& $v)  { }

is equivalent to 

$copy_of_a = $a;
while(next($copy_of_a))
{
  $k = key($copy_of_a);
  $v =& $a[$k];
}

Using =& operator, a new value should be added if it has been unset in
the original array.

Reproduce code:
---------------
$a = array(0,1,2,3,4,5,6,7,8);
$i = 0;
foreach ($a as $k =>& $v)
{
  $v+=100;

  if ($i++==2)
  {
    unset($a[5]);
  }
}
var_dump($a);

Expected result:
----------------
array(8) {
  [0]=>
  int(100)
  [1]=>
  int(101)
  [2]=>
  int(102)
  [3]=>
  int(3)      // modification of values stops here
  [4]=>
  int(4)
  [6]=>
  int(6)
  [7]=>
  int(7)
  [8]=>
  int(8)
}



Actual result:
--------------
array(8) {
  [0]=>
  int(100)
  [1]=>
  int(101)
  [2]=>
  int(102)
  [3]=>
  int(103)
  [4]=>
  int(104)
  [6]=>
  int(106)
  [7]=>
  int(107)
  [8]=>
  int(108)
  [5]=>        // note: the new value should be added here
  int(100)
}




------------------------------------------------------------------------


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