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Date: Tue, 10 Nov 2015 20:45:07 +0100
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To: Philip Hofstetter <phofstetter@sensational.ch>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] PHP7 / foreach / references / ugly code / discrepancy
 to PHP 5.6
From: nikita.ppv@gmail.com (Nikita Popov)

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On Tue, Nov 10, 2015 at 5:48 PM, Philip Hofstetter <
phofstetter@sensational.ch> wrote:

> Hi,
>
> I'm having a cause of slightly ugly code that runs differently from PHP 5.6
> to PHP 7 and I don't think this difference is documented, nor expected. As
> I'm not sure whether this is an intended change or not, I'm asking here
> firstr before making a bug report.
>
> The code in question is
>
> ----
> $b = [1, 2, 3];
>
> foreach($b ?: [] as &$v){
>     $v = $v*2;
>     unset($v);
> }
>
> var_dump($b);
> ----
> in PHP7, this produces
>
> array(3) {
>   [0] =>
>   int(1)
>   [1] =>
>   int(2)
>   [2] =>
>   int(3)
> }
>
> whereas in PHP 5.6 and earlier, this produces
>
> array(3) {
>   [0] =>
>   int(2)
>   [1] =>
>   int(4)
>   [2] =>
>   int(6)
> }
>
> what scares me about this is that in order to get the old behaviour in PHP7
> back, you just have to get rid of the ?: operator:
>
> foreach($b as &$v){
>
> is fine
>
> foreach($b ?: [] as &$v){
>
> is not.
>
> I guess this is related to
>
> http://php.net/manual/en/migration70.incompatible.php#migration70.incompatible.foreach.by-value
>  or
>
> http://php.net/manual/en/migration70.incompatible.php#migration70.incompatible.foreach.by-ref
> ,
> but I'm not entirely sure whether this is actually intended behaviour -
> it's certainly unexpected to me that applying ?: now always makes a copy
> whereas before it didn't.
>

This is a bug in PHP 5, which has been fixed in PHP 7 as a side-effect of
other changes. The new behavior is correct. This issue is tracked at
https://bugs.php.net/bug.php?id=70857.

Nikita

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