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Bug #46724 Floating number is not equal!
Submitted: 2008-12-01 10:06 UTC Modified: 2008-12-09 01:07 UTC
From: yanan at joit dot com Assigned:
Status: Not a bug Package: Unknown/Other Function
PHP Version: 5.2.6 OS: WindowsXP
Private report: No CVE-ID: None
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 [2008-12-01 10:06 UTC] yanan at joit dot com
Description:
------------
<?php
$price = 10.05;
$f_price = $price * 100;
$int_price = floor($f_price); 
var_dump($f_price==$int_price);
?>

The codes below should print 
bool(true)
.But in fact, it prints 
bool(false)
.
The same results appear when $price=10.03 or 10.04.
However, when $price=10.06, it prints
bool(true)
.


Reproduce code:
---------------
<?php
$price = 10.05;
$f_price = $price * 100;
$int_price = floor($f_price); 
var_dump($f_price==$int_price);
?>

Expected result:
----------------
bool(true)

Actual result:
--------------
bool(false)

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 [2008-12-01 10:15 UTC] pajoye@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.


 [2008-12-09 01:07 UTC] yanan at joit dot com
Thank u.
I need to think about a new method to solve my problem...
 
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