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Bug #20688 Math zero
Submitted: 2002-11-27 19:42 UTC Modified: 2003-05-20 04:21 UTC
From: xqcheng at mail dot xjtu dot edu dot cn Assigned:
Status: Not a bug Package: Math related
PHP Version: 4.2.3 OS: windows
Private report: No CVE-ID: None
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 [2002-11-27 19:42 UTC] xqcheng at mail dot xjtu dot edu dot cn 
<?php
$temp=-1.0;
for($i=0;$i<=10;$i++)
{
$temp=$temp+0.2;
echo "<br>".$temp;
}
?>

the output is :

-0.8
-0.6
-0.4
-0.2
-5.55111512313E-017
0.2
0.4
0.6
0.8
1
1.2

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 [2002-11-27 23:18 UTC] alan_k@php.net 
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

there are quite a few bug reports on this.

adding floats can produce unpredicable results
you could try using bcmath or sprintf

$temp=-1.0;
for($i=0;$i<=10;$i++){
$temp=(float) sprintf(\"%.2f\",$temp+0.2);
echo \"<br>\".$temp;
}
 [2003-05-19 13:08 UTC] rmendes at agencyweb dot net 
I have a similar problem :

<?
$a = 0.02;
$b = -0.02;
$total = $a +$b;
echo "$total";
?>

the output is :

Total : 5.55111512313E-017

Why ? and i am forced tio use bcmath ??

Thanks.
 [2003-05-20 04:21 UTC] mgf@php.net 
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

For "why", please see http://www.php.net/language.types.float (the box headed "Floating point precision").

For more help on working with floating point numbers, please try a support forum such as php-general@lists.php.net.
 
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