Bug #75433 [Com]: Possible array indicies regression in array_values

Edit report at https://bugs.php.net/bug.php?id=75433&edit=1 ID: 75433 Comment by: domen at jollydeck dot com Reported by: bourigaultfabien at gmail dot com Summary: Possible array indicies regression in array_values Status: Analyzed Type: Bug Package: Arrays related Operating System: Linux PHP Version: 7.2.0RC4 Assigned To: pollita Block user comment: N Private report: N New Comment: It looks like this regression still affects array_values on empty arrays (arrays which previously had values but values are all unseted before using array_values): https://3v4l.org/U4qRd Previous Comments: ------------------------------------------------------------------------ [2017-10-27 17:09:39] pollita@php.net https://github.com/php/php-src/commit/cc96166f743011c037d9915681b28c363c189e0a should address this (thanks for the catch during pre-release!) Going to keep this open for a bit as array_slice() is impacted by a similar root cause (in 7.3 only) and this is as good a place to track it as any. ------------------------------------------------------------------------ [2017-10-25 02:42:02] requinix@php.net > It looks like calling unset() on one array element and then appending an item to this array > produce a different > result in PHP 7.2+. Close. PHP won't reuse the removed key in any version, even if it was at the end of the array. The problem here is in array_values: https://3v4l.org/vlTD7 > $old = ['one', 'two', 'three', 'four']; > unset($old[3]); Before and after, $old is a particular form of array where it has consecutive integer keys starting from 0 in ascending order ("packed without holes"). In other words, array_keys($old) === range(0, count($old) - 1) https://github.com/php/php-src/blob/php-7.2.0RC4/ext/standard/array.c#L4016 In PHP 7.2 array_values() gained an optimization: for packed no-hole arrays it returns the array as-is because the reindexing would not have changed anything, however it would have reset the value for the next array key by virtue of creating a new array. So it looks like there should be a check added for that as well. (Or maybe it gets bundled into HT_IS_WITHOUT_HOLES?) ------------------------------------------------------------------------ [2017-10-24 20:43:34] bourigaultfabien at gmail dot com Description: ------------ It looks like there are some weird behavior with array indices. If you look at https://3v4l.org/IOvBR the output is is different for PHP 7.2+ (and also for HHVM 3.21+). After looking deeper at what may be wrong I ended to write https://3v4l.org/gG7BG which gives the same output for any PHP version. It looks like calling unset() on one array element and then appending an item to this array produce a different result in PHP 7.2+. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=75433&edit=1