#40755 [NEW]: Increment/Decrement operator calculation oddity

[henson dot garth at gmail dot com]

From: henson dot garth at gmail dot com
Operating system: Linux
PHP version: 5.2.1
PHP Bug Type: Math related
Bug description: Increment/Decrement operator calculation oddity

Description:
------------
The increment/decrement operators seem to calculate out of order compared
to other languages and even previous versions of PHP. I compared this
report numerous times against a 4.3.11 install that I am running to verify
the inconsistency. In the case of PHP 5.2.x, the increment operator seems
to be processed in an inappropriate order to the rest of the statement. In
4.3.11, everything is presented just as expected (as my Expected results
display below).

Reproduce code:
---------------
$a = array(); // Begin Test 1
$b = 0;
$a[$b++] = $b;
var_dump($a);

$a = array(); // Begin Test 2
$b = 0;
$a[$b] = $b++;
var_dump($a);

$a = array(); // Begin Test 3
$b = 10;
$a[$b--] = $b;
var_dump($a);

$a = array(); // Begin Test 4
$b = 10;
$a[$b] = $b--;
var_dump($a);

Expected result:
----------------
array(1){[0] => int(1)}
array(1){[0] => int(0)}
array(1){[10] => int(9)}
array(1){[10] => int(10)}

Actual result:
--------------
array(1){[0] => int(1)}
array(1){[1] => int(0)}
array(1){[10] => int(9)}
array(1){[9] => int(10)}

--
Edit bug report at [url]http://bugs.php.net/?id=40755&edit=1[/url]
--
Try a CVS snapshot (PHP 4.4): [url]http://bugs.php.net/fix.php?id=40755&r=trysnapshot44[/url]
Try a CVS snapshot (PHP 5.2): [url]http://bugs.php.net/fix.php?id=40755&r=trysnapshot52[/url]
Try a CVS snapshot (PHP 6.0): [url]http://bugs.php.net/fix.php?id=40755&r=trysnapshot60[/url]
Fixed in CVS: [url]http://bugs.php.net/fix.php?id=40755&r=fixedcvs[/url]
Fixed in release: [url]http://bugs.php.net/fix.php?id=40755&r=alreadyfixed[/url]
Need backtrace: [url]http://bugs.php.net/fix.php?id=40755&r=needtrace[/url]
Need Reproduce Script: [url]http://bugs.php.net/fix.php?id=40755&r=needscript[/url]
Try newer version: [url]http://bugs.php.net/fix.php?id=40755&r=oldversion[/url]
Not developer issue: [url]http://bugs.php.net/fix.php?id=40755&r=support[/url]
Expected behavior: [url]http://bugs.php.net/fix.php?id=40755&r=notwrong[/url]
Not enough info: [url]http://bugs.php.net/fix.php?id=40755&r=notenoughinfo[/url]
Submitted twice: [url]http://bugs.php.net/fix.php?id=40755&r=submittedtwice[/url]
register_globals: [url]http://bugs.php.net/fix.php?id=40755&r=globals[/url]
PHP 3 support discontinued: [url]http://bugs.php.net/fix.php?id=40755&r=php3[/url]
Daylight Savings: [url]http://bugs.php.net/fix.php?id=40755&r=dst[/url]
IIS Stability: [url]http://bugs.php.net/fix.php?id=40755&r=isapi[/url]
Install GNU Sed: [url]http://bugs.php.net/fix.php?id=40755&r=gnused[/url]
Floating point limitations: [url]http://bugs.php.net/fix.php?id=40755&r=float[/url]
No Zend Extensions: [url]http://bugs.php.net/fix.php?id=40755&r=nozend[/url]
MySQL Configuration Error: [url]http://bugs.php.net/fix.php?id=40755&r=mysqlcfg[/url]

[derick@php.net]

ID: 40755
Updated by: [email]derick@php.net[/email]
Reported By: henson dot garth at gmail dot com
-Status: Open
+Status: Bogus
Bug Type: Math related
Operating System: Linux
PHP Version: 5.2.1
New Comment:

Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
[url]http://www.php.net/manual/[/url] and the instructions on how to report
a bug at [url]http://bugs.php.net/how-to-report.php[/url]

Using and modifying the same variable when using post/pre-
decrement/increment is undefined (and not only in PHP).


Previous Comments:
------------------------------------------------------------------------

[2007-03-08 01:43:13] henson dot garth at gmail dot com

Description:
------------
The increment/decrement operators seem to calculate out of order
compared to other languages and even previous versions of PHP. I
compared this report numerous times against a 4.3.11 install that I am
running to verify the inconsistency. In the case of PHP 5.2.x, the
increment operator seems to be processed in an inappropriate order to
the rest of the statement. In 4.3.11, everything is presented just as
expected (as my Expected results display below).

Reproduce code:
---------------
$a = array(); // Begin Test 1
$b = 0;
$a[$b++] = $b;
var_dump($a);

$a = array(); // Begin Test 2
$b = 0;
$a[$b] = $b++;
var_dump($a);

$a = array(); // Begin Test 3
$b = 10;
$a[$b--] = $b;
var_dump($a);

$a = array(); // Begin Test 4
$b = 10;
$a[$b] = $b--;
var_dump($a);

Expected result:
----------------
array(1){[0] => int(1)}
array(1){[0] => int(0)}
array(1){[10] => int(9)}
array(1){[10] => int(10)}

Actual result:
--------------
array(1){[0] => int(1)}
array(1){[1] => int(0)}
array(1){[10] => int(9)}
array(1){[9] => int(10)}


------------------------------------------------------------------------


--
Edit this bug report at [url]http://bugs.php.net/?id=40755&edit=1[/url]