ID: 45897
User updated by: hengkhee at gmail dot com
Reported By: hengkhee at gmail dot com
Status: Bogus
Bug Type: Math related
Operating System: UBuntu 8.04, CentOS 5.0
PHP Version: 5.2.4
New Comment:
Thank you for your reply,
I still not very clear about why this happen, as for a PHP beginner,
the arithmetic below is very straight, but output the unexpected
result:
$var1 = 0.15 * 3 * 100;
$var2 = $var1 + 1.0 - 1.0; #Perform some dummy matematic operation
$var3 = $var2 % 5;
var_dump($var3); # Still unexpected result, int(4)
For same arithmetic, Java is ok:
float f, result;
f = (float)(0.15 * 3 * 100);
result = f%5;
System.out.println(result);
My question is:
- Don't PHP processor should handle this situation?
- So this consider not a bug of PHP? Or is weaknesses of it?
- Any work around? My work around is concat an string with the
variable..
May be it is a stupid way, but it works fine for me (until current
version of PHP).
Thank you for your discussion and advice, I really appreaciated.
Previous Comments:
------------------------------------------------------------------------
[2008-08-26 22:41:54] [EMAIL PROTECTED]
Floating point values have a limited precision. Hence a value might
not have the same string representation after any processing. That also
includes writing a floating point value in your script and directly
printing it without any mathematical operations.
If you would like to know more about "floats" and what IEEE
754 is, read this:
http://docs.sun.com/source/806-3568/ncg_goldberg.html
Thank you for your interest in PHP.
$ php -dprecision=32 -r 'var_dump(0.15*3*100);'
float(44.999999999999992894572642398998)
------------------------------------------------------------------------
[2008-08-23 13:14:38] hengkhee at gmail dot com
The php version on
------------
Ubuntu 8.04:
------------
PHP 5.2.4-2ubuntu5.3 with Suhosin-Patch 0.9.6.2 (cli) (built: Jul 23
2008 06:46:18)
Copyright (c) 1997-2007 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2007 Zend Technologies
------------
CentOS:
------------
PHP 5.2.6 (cli) (built: Jul 29 2008 20:48:49)
Copyright (c) 1997-2008 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2008 Zend Technologies
with Zend Extension Manager v1.2.2, Copyright (c) 2003-2007, by
Zend Technologies
with Zend Optimizer v3.3.3, Copyright (c) 1998-2007, by Zend
Technologies
------------------------------------------------------------------------
[2008-08-23 13:09:02] hengkhee at gmail dot com
Description:
------------
- Modulus error, please refer to code.
- Using default package/installation from Ubuntu 8.04 Server/Desktop
and CentOS 5.0
- Using default php.ini from distro.
Reproduce code:
---------------
$var1 = 0.15 * 3 * 100;
echo ($var1 % 5); # Output "4", unexpected result
echo ((0.15 * 3 * 100) % 5); # Output "4", unexpected result
echo (45.00 % 5); # Output "0", correct result
echo (45 % 5); # Output "0", correct result
echo (($var1."") % 5); # Output "0", correct result
Expected result:
----------------
Correct result = "0" for all above sample.
Actual result:
--------------
Please refer to above sample code.
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=45897&edit=1
