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Bug #45712 $something == NaN returns true with 5.3, false with 5.2.*
Submitted: 2008-08-05 02:39 UTC Modified: 2014-02-15 23:12 UTC
Votes:2
Avg. Score:3.0 ± 0.0
Reproduced:0 of 0 (0.0%)
From: for-bugs at hnw dot jp Assigned: tony2001 (profile)
Status: Closed Package: Variables related
PHP Version: 5.2CVS, 5.3CVS, 6CVS (2008-08-05) OS: *
Private report: No CVE-ID: None
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 [2008-08-05 02:39 UTC] for-bugs at hnw dot jp 
Description:
------------
There is == operator's problem dealing with NaN(Not a Number) in PHP 5.3.0alpha1. This behavior is different with PHP 5.0.0-5.2.6, so this is compatibility problem.

Reproduce code:
---------------
<?php

$nan = (-1e300*1e300)/(1e300*1e300); // float(NAN)

var_dump($nan=='');
var_dump($nan==0.5);
var_dump($nan==50);
var_dump($nan=='500');
var_dump($nan=='abc');
var_dump($nan==$nan);

Expected result:
----------------
bool(false)
bool(false)
bool(false)
bool(false)
bool(false)
bool(false)

Actual result:
--------------
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)

Patches

Pull Requests

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 [2008-08-05 12:33 UTC] jani@php.net 
That $nan == $nan should be true. (like it is with 5.3)
 [2008-08-05 12:52 UTC] for-bugs at hnw dot jp 
NaN is not exact number. So, NaN should not equals itself. Additionaly, NaN == NaN is false in C. You can see behavior of C as follows.

$ cat nan.c
int main() {double d;d=(-1e300*1e300)/(1e300*1e300);if (d==d) return 1; else return 2;}
$ gcc nan.c; ./a.out; echo $?
2
$
 [2008-08-07 07:37 UTC] tony2001@php.net 
I'm testing a patch for it.
 [2008-08-07 08:36 UTC] tony2001@php.net 
This bug has been fixed in CVS.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.
 [2010-07-28 01:28 UTC] jwvdveer at gmail dot com 
Please, reopen this bug. It's not working in PHP 5.3.3 on Windows platform (released at 2010-07-21).
The behaviour of a comparison to NAN is the same as noted here.

It's not just a `me too`, but this thread shouln't have been closed.
 [2011-05-26 07:59 UTC] philip@php.net
-Status: Closed +Status: Re-Opened
 [2011-05-26 07:59 UTC] philip@php.net 
Reopening because the associated test tests INF as well. However, this is about INF:

// 5.3.7-dev (and all past PHP versions, afaict)
$inf = pow(0,-2); var_dump($inf==$inf); var_dump($inf===$inf); // false true

// 5.4.0-dev
$inf = pow(0,-2); var_dump($inf==$inf); var_dump($inf===$inf); // true true

Please explain.

And @jwvdveer, it was indeed fixed (in 5.3) and made to return false.
 [2013-09-16 16:48 UTC] cmbecker69 at gmx dot de 
> Please explain.

It seems there was a bug *before* PHP 5.4, because if $a === $b,
then $a == $b by definition.
 [2014-02-15 23:12 UTC] nikic@php.net
-Status: Re-Opened +Status: Closed
 
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