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Bug #63074 Intval doesn't return exact value
Submitted: 2012-09-12 16:10 UTC Modified: 2012-09-12 16:42 UTC
From: berthonneau dot olivier at gmail dot com Assigned:
Status: Not a bug Package: Math related
PHP Version: 5.3.16 OS: Windows Server 2008 and Ubuntu
Private report: No CVE-ID: None
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From: berthonneau dot olivier at gmail dot com
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 [2012-09-12 16:10 UTC] berthonneau dot olivier at gmail dot com
Description:
------------
Hi!

I found a strange bug today.
I have a float variable which contains 3876.0000, I want to pass it through the 
intval() function.
I know it's already an integer because there is no decimals, but the strange thing 
is that intval() don't return 3876 but 3875.

I experience the same thing with explicite cast.

Test script:
---------------
$tmp = 1370 * 1.15;
echo $tmp . "<br />"; // echo 3875.5
$tmp += 0.5;
echo $tmp . "<br />"; // echo 3876
$tmp = intval($tmp);
echo "tmp= ". $tmp . "<br />"; // echo 3875

========

Same thing with an explicite cast: $tmp = (int)$tmp;

Expected result:
----------------
I expect that the last echo output 3876

Actual result:
--------------
The last echo output 3875 instead of 3876.

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 [2012-09-12 16:42 UTC] rasmus@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://www.floating-point-gui.de/

Thank you for your interest in PHP.


 [2012-09-12 16:42 UTC] rasmus@php.net
-Status: Open +Status: Not a bug
 
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