Doc->Bug #71030 [Ver->Asn]: PHP 7.0 list() behavior

Edit report at https://bugs.php.net/bug.php?id=71030&edit=1 ID: 71030 Updated by: bwoebi@php.net Reported by: filippo dot desantis at gmail dot com Summary: PHP 7.0 list() behavior -Status: Verified +Status: Assigned -Type: Documentation Problem +Type: Bug Package: *General Issues Operating System: OSX PHP Version: 7.0.0 -Assigned To: +Assigned To: nikic Block user comment: N Private report: N New Comment: The implementation is definitely not matching the RFC here. In current code the case of list($a, $b) = $a; is special cased (basically when the RHS variable occurs on the LHS). In that case we do a quick (COW) copy first. Though, try: $a = [1, 2]; $_a = "a"; list($$_a, $b) = $a; // variable variable # or $c = &$a; list($c, $b) = $a; // with reference then you'll get what's expected as per the RFC. I wonder though whether we really should have a special case here … either for all or for none? Assigning to Nikita (RFC author) so that he can clarify... Previous Comments: ------------------------------------------------------------------------ [2015-12-05 01:36:28] requinix@php.net https://3v4l.org/vBGTH It looks like the RHS variable does not get reevaluated. This is the behavior that would make the most sense to me, but it does contradict what the AST RFC says. I haven't found any talk about changing how list() works post-RFC. So either a) list() is not behaving correctly, or b) The warning can be removed and the migration guide needs to mention the change ------------------------------------------------------------------------ [2015-12-04 16:41:23] filippo dot desantis at gmail dot com Description: ------------ I'm using PHP 7.0.0 (cli) (built: Dec 2 2015 13:35:31) Zend Engine v3.0.0, Copyright (c) 1998-2015 Zend Technologies Running the example in the RFC https://wiki.php.net/rfc/abstract_syntax_tree for the list() function $a = [1, 2]; list($a, $b) = $a; // OLD: $a = 1, $b = 2 // NEW: $a = 1, $b = null + "Undefined index 1" I don't get the "NEW" result but the "OLD" one. Looking for some more information I found in the documentation (http://php.net/list) the warning "Modification of the array during list() execution (e.g. using list($a, $b) = $b) results in undefined behavior.". I was wondering which of the two behaviour should be the good one :) Test script: --------------- <?php $a = [1, 2]; list($a, $b) = $a; var_dump($a, $b); ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=71030&edit=1