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Bug #45145 reference aliasing is working backwards, wiping the var
Submitted: 2008-06-01 14:35 UTC Modified: 2008-06-02 14:07 UTC
From: phpbug at thoria dot org Assigned:
Status: Not a bug Package: Variables related
PHP Version: 5.2CVS-2008-06-01 (snap) OS: Linux
Private report: No CVE-ID: None
View Developer Edit
 [2008-06-01 14:35 UTC] phpbug at thoria dot org 
Description:
------------
On versions 5.2.3 and 4.3.1(Zend off), on different shared hosting servers.

Within one large function/loop in my app

$x = &$y;

y is destroyed and replaced by x, intermittently. unset($x) is ignored if placed above it, and x still goes into y. There is no workaround, besides using $x = $y. I think any ref assignments in this loop behave like this if $x has had a prior value.

You will need to have my whole app installed. It's so weird, it makes me feel dumb to submit it.

Reproduce code:
---------------
$bb = "original string";
$aa = "moo";
unset($aa);
$aa = &$bb;
echo "AA->$aa, BB->$bb <br>";

or

$bb = "original string";
$aa = "moo";
$aa = &$bb;
echo "AA->$aa, BB->$bb <br>";

The following is OK

$aa = "moo";
$bb = "original string";
$aa = &$bb;
echo "AA->$aa, BB->$bb <br>";

Expected result:
----------------
AA->original string, BB->original string 
AA->original string, BB->original string 
AA->original string, BB->original string 

Actual result:
--------------
AA->original string, BB->original string 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->original string, BB->original string 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->original string, BB->original string 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->original string, BB->original string 
AA->moo, BB->

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 [2008-06-02 08:34 UTC] phpbug at thoria dot org 
Now, I'm really scratching my head. After hacking my code down for hours, I realised it could be replicated in a few lines. Iteration 1 is OK. Iteration 2 produces the effect. The unset is not necessary. Iteration 3 shows how it goes away if $x='moo' is declared first.

<?php

echo "1<br>";

$y = "original string";
$x = "moo";
unset($x);
$x = &$y;
echo "X $x  Y $y<br><br>";

echo "2<br>";

$y = "original string";
$x = "moo";
unset($x);
$x = &$y;
echo "X $x  Y $y<br><br>";

echo "3<br>";

$x = "moo";
$y = "original string";
$x = &$y;
echo "X $x  Y $y<br><br>";

?>
 [2008-06-02 08:56 UTC] phpbug at thoria dot org 
Arrrhhh. I'm just guilty of C-thinking.
 [2008-06-02 14:07 UTC] phpbug at thoria dot org 
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