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Bug #31513 wrong expression execution order
Submitted: 2005-01-12 11:58 UTC Modified: 2005-01-12 13:30 UTC
From: dan at yes dot lt Assigned:
Status: Not a bug Package: *General Issues
PHP Version: 5.0.3 OS: any
Private report: No CVE-ID: None
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 [2005-01-12 11:58 UTC] dan at yes dot lt 
Description:
------------
Arithmetic expression execution returns unexpected results with ++ or -- operators.

Reproduce code:
---------------
$a = 10;   
$c = $a++ + ++$a;
echo "$c\n";

$a = 10;
$c = ++$a + $a++;
echo "$c\n";

Expected result:
----------------
22
22

Actual result:
--------------
22
23 <- ?? Why ??

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 [2005-01-12 12:53 UTC] derick@php.net 
You can never rely on this behavior, not in any language that I know about. Do not use the post/pre inc operation in assignments like this.
 [2005-01-12 13:17 UTC] dan at yes dot lt 
<?php

$a = 10;  

$b = &$a;

$a = 10;  
$c = $a++ + ++$a; // Gauname 22, kaip ir turi buti
echo "$c\n\n";


$a = 10;
$c = ++$a + $a++; // Gauname 23, nors turetu buti 22
echo "$c\n\n";

?>
 [2005-01-12 13:18 UTC] dan at yes dot lt 
it works if there is no $b =&$a reference, and fails, if there is that reference...
 [2005-01-12 13:30 UTC] derick@php.net 
Please read me explanation again.
 
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