Bug #60534 [Dup]: Iterating an array twice w and w/o references changes last item to second last

Edit report at https://bugs.php.net/bug.php?id=60534&edit=1 ID: 60534 Updated by: requinix@php.net Reported by: aron dot cederholm at gmail dot com Summary: Iterating an array twice w and w/o references changes last item to second last Status: Duplicate Type: Bug Package: Arrays related Operating System: Arch Linux PHP Version: 5.3.8 Block user comment: N Private report: N New Comment: @supplier: It's not a quirk. It's a reference. A natural consequence of the fact that PHP does not have block scopes. Protip: if you think the answer to a problem is to use a reference, think again. Previous Comments: ------------------------------------------------------------------------ [2020-08-28 03:32:42] supplier at enex dot net Can anyone please provide an example of how this unusual behaviour might be useful? Having pulled my hair out (like many others no doubt) it seems odd that this behaviour persists unless there is an obvious point to it (other than to separate the super-geeks from the lesser-geeks) For super-geeking there is always the standard for loop, so if there is a reason to punish us lesser geeks with this foreach quirk please advise what the use-case is. thanks a million! ------------------------------------------------------------------------ [2011-12-15 17:09:50] anon at anon dot anon This gets submitted as a bug about twice a month. It's still not a bug. After the first loop finishes $a is a reference to the last element of the array. That means that during the second loop, the last value of the array is constantly being modified by the loop. Once it gets to the last element, 'd' has been overwritten already. foreach ($array as &$a) { echo "($a): " . join(',', $array) . "\n"; } foreach ($array as $a) { echo "($a): " . join(',', $array) . "\n"; } (a): a,b,c,d (b): a,b,c,d (c): a,b,c,d (d): a,b,c,d (a): a,b,c,a (b): a,b,c,b (c): a,b,c,c (c): a,b,c,c As it says in the manual, unset() after foreach'ing by reference: http://www.php.net/manual/en/control-structures.foreach.php ------------------------------------------------------------------------ [2011-12-15 15:15:12] aron dot cederholm at gmail dot com Description: ------------ Iterating an array twice, first time with references, second time *without* references, will trigger a bug in the second iteration where the last item of the array is overwritten by the second last item in the array. This seem to be the same bug as #46123, which was dismissed on erroneous grounds Test script: --------------- <? # For a more verbose look at this bug, watch http://pastebin.com/gq2qekYh $array = array('a', 'b', 'c', 'd'); # testing array foreach ($array as &$a) {} foreach ($array as $a) {} echo join(',', $array); # will produce a,b,c,c *not* a,b,c,d as expected die(); ## while, these will work as expected # 1 foreach ($array as $a) {} print_r($array); die(); # 2 foreach ($array as &$a) {} print_r($array); die(); # 3 foreach ($array as &$a) {} foreach ($array as &$a) {} print_r($array); die(); # 4 foreach ($array as $a) {} foreach ($array as $a) {} print_r($array); die(); # 5 foreach ($array as $a) {} foreach ($array as &$a) {} print_r($array); die(); ?> Expected result: ---------------- a,b,c,d Actual result: -------------- a,b,c,c ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=60534&edit=1