Bug #80161 [Nab]: Iterating on key/value with reference (&) has unexpected side effect

Edit report at https://bugs.php.net/bug.php?id=80161&edit=1 ID: 80161 Updated by: cmb@php.net Reported by: g dot passault at gmail dot com Summary: Iterating on key/value with reference (&) has unexpected side effect Status: Not a bug Type: Bug Package: Arrays related Operating System: Linux (Ubuntu 18.04) PHP Version: 7.4.10 Assigned To: cmb Block user comment: N Private report: N New Comment: It might be best to forward this feature request to the internals mailing list[1], since this bugtracker isn't really suitable for discussions. [1] <https://www.php.net/mailing-lists.php#internals> Previous Comments: ------------------------------------------------------------------------ [2020-09-29 21:02:56] g dot passault at gmail dot com Imagine foreach($x as $y) would implicitely performs unset($y) beforehand, that would fix this broken behaviour, and what legitimate code would be impacted with such a change? ------------------------------------------------------------------------ [2020-09-29 16:05:00] cmb@php.net > However I'm not sure if assigning a value to a variable that is > a reference through the "as" of a foreach is a good behaviour There is nothing special about that assignment; it's a reference assignment, if the variable is already a reference. If you have to use references in foreach loops, and you need the loop variable later on, consider to unset() it after the loop. See also the warning on <https://www.php.net/manual/en/control-structures.foreach.php>. ------------------------------------------------------------------------ [2020-09-29 15:50:30] fghghghgh at fgfgfg dot com there is nothing unexpected, that's how references are working http://schlueters.de/blog/archives/125-Do-not-use-PHP-references.html ------------------------------------------------------------------------ [2020-09-29 15:48:28] g dot passault at gmail dot com Actually, I understand the reason why this behaves like that, since at the end of the first foreach loop $item is a reference to the last item in the array However I'm not sure if assigning a value to a variable that is a reference through the "as" of a foreach is a good behaviour This issue actually happened in a script I wrote and I was surprised with result, what I mean is that I can easily real life example why one would walk an array and change it, and then walk it again to read it, but not real life example of assigning a value with the first iteration of a loop through the "as" of foreach. ------------------------------------------------------------------------ [2020-09-29 15:43:53] g dot passault at gmail dot com Description: ------------ For some reason, walking an array using keys and reference values (&), even without doing anything with it and then walking it has an influence if and only if the variable name is the same in both cases Test script: --------------- <?php $array = [ 'x' => 1, 'y' => 2, 'z' => 3 ]; // This useless walk has an effect on below walk foreach ($array as &$item) {} // This will show 1 2 2 instead of 1 2 3 // If you use another name for $item variable, it will show 1 2 3 foreach ($array as $item) { echo $item."\n"; } Expected result: ---------------- 1 2 3 Actual result: -------------- 1 2 2 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=80161&edit=1