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Bug #73622 Foreach iteration with a previously initialized variable
Submitted: 2016-11-30 09:09 UTC Modified: 2016-12-01 13:13 UTC
From: dorin dot marcoci at gmail dot com Assigned:
Status: Not a bug Package: Scripting Engine problem
PHP Version: 7.0.13 OS:
Private report: No CVE-ID: None
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 [2016-11-30 09:09 UTC] dorin dot marcoci at gmail dot com 
Description:
------------
Script below output A A instead of A B.
Is this as designed?

If I do unset($Item) before second foreach then it works as expected.

Test script:
---------------
<?php

$Items = [['Code' => 'A'], ['Item' => 'B']];

foreach ($Items as &$Item)
    $Item['Hash'] = rand(1, 10);

foreach ($Items as $Item)
    echo ' '.$Item['Code'];


Expected result:
----------------
A B

Actual result:
--------------
A A

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 [2016-11-30 09:12 UTC] requinix@php.net
-Status: Open +Status: Not a bug -Package: PHP Language Specification +Package: Scripting Engine problem
 [2016-11-30 09:12 UTC] requinix@php.net 
Please take note of the big red warning in the documentation.
http://php.net/manual/en/control-structures.foreach.php
 [2016-11-30 09:24 UTC] dorin dot marcoci at gmail dot com 
OK, big red warning is not an excuse. This IS definitely a bug.

When I do foreach($Array AS $VAR) then it should return in var a NEW $VAR instance  in any way, was it used previously or not.
 [2016-12-01 07:22 UTC] a at b dot c dot de 
So you want variable references in this particular instance to behave differently from the way they behave in the rest of the language? Not gonna happen.
 [2016-12-01 13:13 UTC] dorin dot marcoci at gmail dot com 
The problem is that foreach performs differently.

This script:

<?php

$A = new stdClass();
$A->Code = 'one';

$B = new stdClass();
$B->Code = 'two';

$H = [$A, $B];
$C = &$A;

foreach ($H as $C) 
	echo ' '.$C->Code;

?>

Outputs: " one two", even if $C initially was a reference.

BUT this one:

<?php

$A = new stdClass();
$A->Code = 'one';

$B = new stdClass();
$B->Code = 'two';

$H = [$A, $B];

foreach ($H as &$C);

foreach ($H as $C) 
	echo ' '.$C->Code;

?>

Outputs: " one one", Surprise!.
 [2016-12-20 07:54 UTC] a at b dot c dot de 
<?php

$A = 'one';

$B = 'two';

$H = [$A, $B];

 foreach ($H as &$C);

foreach ($H as $C) 
echo ' '.$C;

echo "\n$A $B\n" . join(" ", $H);

?>
Is equivalent to
<?php

$A = 'one';

$B = 'two';

$H = [$A, $B];

for($i = 0; $i < count($H); $i++)
{
 $C = &$H[$i];
}

for($i = 0; $i < count($H); $i++)
{
	$C = $H[$i];
	echo ' '.$C;
}

echo "\n$A $B\n" . join(" ", $H);
?>

And is therefore equivalent to:

<?php

$A = 'one';

$B = 'two';

$H = [$A, $B];

$C = &$H[0];
$C = &$H[1];

$C = $H[0];
echo ' '.$C;
$C = $H[1];
echo ' '.$C;

echo "\n$A $B\n" . join(" ", $H);
?>

So with "$C = &$H[1];" $C is set as a reference to the 1st element of H. Then the value of the 0th element of $H is assigned to it (and therefore, by reference, the 1st element of $H). Then the 1st element of $H (which now has the same value as the 0th element) is assigned to it (which has no effect because the 1st element of H already has the same value as the 1st element of H).
 
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