Edit report at http://bugs.php.net/bug.php?id=52315&edit=1
ID: 52315
Comment by: wisent at yandex dot ru
Reported by: wisent at yandex dot ru
Summary: Error in type convert after specific round() operation
Status: Bogus
Type: Bug
Package: Math related
Operating System: Ubuntu 8.04
PHP Version: 5.2.13
New Comment:
aharvey, the problem is not related with strings.
I better should write the code like this:
// this works bad:
$sum = 4926.11;
$sum = round($sum, 2) * 100;
var_dump($sum); // float(492611)
$sum = (integer) $sum;
var_dump($sum); // int(492610)
// the first numbers, the other round() operation, works good
$sum = 4926.11;
$sum = round($sum * 100);
var_dump($sum); // float(492611)
$sum = (integer) $sum;
var_dump($sum); // int(492611)
You probably haven't noticed the main point. After operations on
variable with round() function variables have the same representation,
float(492611). But the subsequent type conversion to integer returns
different values, int(492610) and int(492611).
Previous Comments:
------------------------------------------------------------------------
[2010-07-13 18:27:12] ahar...@php.net
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.
------------------------------------------------------------------------
[2010-07-12 14:40:58] wisent at yandex dot ru
Description:
------------
First I perform specific round() operation. Then I convert the number
from float to integer. The result is wrong, the number differs by 1 from
what it should be.
The problem appears not for every number.
Test script:
---------------
// this works bad:
$sum = '4926.11';
$sum = round($sum, 2) * 100;
var_dump($sum); // float(492611)
$sum = (integer) $sum;
var_dump($sum); // int(492610)
// the same round() operation, the other number, works good
$sum = '426.11';
$sum = round($sum, 2) * 100;
var_dump($sum); // float(42611)
$sum = (integer) $sum;
var_dump($sum); // int(42611)
// the first numbers, the other round() operation, works good
$sum = '4926.11';
$sum = round($sum * 100);
var_dump($sum); // float(492611)
$sum = (integer) $sum;
var_dump($sum); // int(492611)
------------------------------------------------------------------------
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Edit this bug report at http://bugs.php.net/bug.php?id=52315&edit=1
