Bug #76662 [Opn->Nab]: Issue sorting when values are equal

Edit report at https://bugs.php.net/bug.php?id=76662&edit=1 ID: 76662 Updated by: requinix@php.net Reported by: panin dot alexei at gmail dot com Summary: Issue sorting when values are equal -Status: Open +Status: Not a bug Type: Bug -Package: *General Issues +Package: Arrays related Operating System: OSX and UBUNTU PHP Version: 7.0.31 Block user comment: N Private report: N New Comment: 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 http://php.net/manual/en/function.usort.php > Note: > If two members compare as equal, their relative order in the sorted array is undefined. PHP does not guarantee a stable sort. Your example should compare the [0] elements as a secondary sort. return ($a[1] <=> $b[1]) ?: ($a[0] - $b[0]); // $a[0] <=> $b[0] would compare as strings Previous Comments: ------------------------------------------------------------------------ [2018-07-25 08:01:17] panin dot alexei at gmail dot com Description: ------------ --- From manual page: http://www.php.net/function.usort --- Even when values are equal, they are mixed. The resulting / sorted array should be identical with initial array, it;s not the case. Test script: --------------- <?php $array = [ ["1", 1], ["2", 1], ["3", 1], ["4", 1], ["5", 1], ["6", 1], ["7", 1], ["8", 1], ["9", 1], ["10", 1], ["11", 1], ["12", 1], ["13", 1], ["14", 1], ["15", 1], ["16", 1], ["17", 1], ["18", 1], ["19", 1], ["20", 1], ["21", 1], ["22", 1], ["23", 1], ["24", 1], ["25", 1], ["26", 1], ["27", 1], ["28", 1], ["29", 1], ["30", 1], ["31", 1], ["32", 1], ["33", 1], ["34", 1], ["35", 1], ["36", 1] ]; usort($array, function($a, $b){ return $a[1] <=> $b[1]; }); print_r($array); Expected result: ---------------- array should bot be altered Actual result: -------------- array is sorted ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=76662&edit=1