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Bug #50582 Incorrect foreach iteration by value after iteration by reference
Submitted: 2009-12-26 22:48 UTC Modified: 2009-12-27 04:52 UTC
From: mwacker at cornellsun dot com Assigned:
Status: Not a bug Package: Arrays related
PHP Version: 5.3.1 OS: Ubuntu 9.10
Private report: No CVE-ID: None
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 [2009-12-26 22:48 UTC] mwacker at cornellsun dot com 
Description:
------------
A variable acts weird when it is used as a reference variable inside a foreach loop and then as a regular variable inside a foreach loop.
(Originally seen in 5.2.10-2ubuntu6.3, repro'd in a fresh 5.3.1 install)

Reproduce code:
---------------
$ii = array(1, 2, 3);
foreach ($ii as &$i) echo $i;
foreach ($ii as $i) echo $i;

Expected result:
----------------
123123

Actual result:
--------------
123122

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 [2009-12-26 23:25 UTC] pierrick@php.net 
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php
 [2009-12-27 04:52 UTC] rasmus@php.net 
It doesn't act weird.  There is no block scope in PHP, so at the end of 
the first loop $i is a reference to the last element of $ii and in the 
second loop you are now assigning values to that reference which means 
you are overwriting the 3rd element of $ii each time through the loop.  
That of course means that once you get to the 3rd element of $ii it is 
no longer 3 and you see the last value assigned to it, which was 2.
 [2014-03-21 08:12 UTC] tri at iki dot fi 
In my opinion it is definitely a bug. I can understand why it can be called a feature, but the foreach semantics should be defined so that loop variable is unset (meaningful only if the value happens to be a reference) before the loop construct starts to assign values to it.

This is source of weird and subtle bugs.
 
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