Bug #72173 [Opn->Nab]: very strange reference behavior (bug?) in PHP 5.6, 7.0

Edit report at https://bugs.php.net/bug.php?id=72173&edit=1 ID: 72173 Updated by: requinix@php.net Reported by: cf0hay at gmail dot com Summary: very strange reference behavior (bug?) in PHP 5.6, 7.0 -Status: Open +Status: Not a bug Type: Bug Package: Arrays related Operating System: Linux 64bit PHP Version: 7.0.6 Block user comment: N Private report: N New Comment: https://3v4l.org/q3MhC and https://3v4l.org/e4Q81 respectively. Close, but there's two details missing from your explanation: 1. Assignment of arrays copies the contents of the array, not its values. Semantics. 2. $x[2] and $orig[0] are not values themselves anymore but references to values. That means copying $b=$x and $copy=$orig will result in a copy of the reference: a different reference itself though indicating the same referenced value. Here's a PHP analogy of what happens under the hood: - https://3v4l.org/MrNID $x and $b - https://3v4l.org/GS6sU $orig and $copy (I suggest this one first) Previous Comments: ------------------------------------------------------------------------ [2016-05-07 14:35:07] cf0hay at gmail dot com Short version of the bug: <?php $orig = [1]; $ref =& $orig[0]; $copy = $orig; $orig[0] = 10; var_dump($copy[0]); //returns 10, should return 1 ------------------------------------------------------------------------ [2016-05-07 14:25:00] cf0hay at gmail dot com I consider this a bug, because with integer references this doesn't happen: <?php $a = 5; $ref =& $a; //$ref points to the same value as $a $ref += 100; //$ref and $a are both 105 because of this $b = $a; //this copies the value 105 to a new place $ref += 100; //$ref and $a are 205, but $b remains 105 correctly var_dump($b); ------------------------------------------------------------------------ [2016-05-07 14:16:52] cf0hay at gmail dot com Description: ------------ Affects both PHP 5.6.21 and PHP 7.0.6 . - Create an array with some elements - Iterate over this array by reference - assign (copy) this array by value to a different variable - Iterate over the previous array by reference again using the same variable - the copied array changes at the value which was the last of the original one Test script: --------------- <?php $x = [1,2,3]; foreach($x as &$ref){ $ref += 100; } /* $x === [101, 102, 103] at this point, $ref is bound to the last element of $x, that's OK */ $b = $x; /* this should logically copy $x to $b *by value* (COW happens) */ $b[0] = 0; /* this should force an array copy in memory */ /* here, $ref should be rebound to the elements of $x by reference */ foreach($x as &$ref){ $ref += 100; } /* at this point, $x === [201, 202, 203] which is correct, $ref refers to the last element of $x again, which is OK, BUT! As we copied $b by value before, is should stay as is, but the last element of $b changes to 203! */ var_dump($b); Expected result: ---------------- array(3) { [0]=> int(0) [1]=> int(102) [2]=> int(103) } Actual result: -------------- array(3) { [0]=> int(0) [1]=> int(102) [2]=> &int(203) } ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=72173&edit=1