From: jsbruns at selectionsheet dot com
Operating system: Windows NT Server
PHP version: 5.2.1
PHP Bug Type: Math related
Bug description: Subtracting 2 floats returns incorrect results
Description:
------------
Attempting to subtract one floating point number from another returns the
incorrect result. Float 1 is assigned in the code, float 2 is retrieved
from a mysql DB field, which is of type DECIMAL(5,4).
When subtracting $float1 from $float2 the result is:
-7.105427357601E-015
Reproduce code:
---------------
//Field discount2 is defined as type DECIMAL(5.4). Original value in
database is 0.56, use PHP to multiply by 100 to get a whole number (56).
$result = mysql_query("SELECT `discount2`
FROM `product_discounts`
WHERE `product_id` = 'prod1'");
$discount2 = mysql_result($result)*100;
$discount1 = 56;
echo $discount1; //56
echo $discount2; //56
if ($discount2 != $discount1)
echo "Discount1 not equal to Discount2"; //Y
if (bccomp($discount1,$discount2) == 0)
echo "Discount1 equal to Discount2"; //Y
echo ($discount1 + $discount2); //112
echo ($discount1 - $discount2); //-7.105427357601E-015
Expected result:
----------------
When subtracting $discount1 from $discount2 I expected to get 0. When
adding the two I get the expected 112.
Actual result:
--------------
When subtracting $discount1 from $discount2 I get:
-7.105427357601E-015
--
Edit bug report at http://bugs.php.net/?id=41213&edit=1
--
Try a CVS snapshot (PHP 4.4):
http://bugs.php.net/fix.php?id=41213&r=trysnapshot44
Try a CVS snapshot (PHP 5.2):
http://bugs.php.net/fix.php?id=41213&r=trysnapshot52
Try a CVS snapshot (PHP 6.0):
http://bugs.php.net/fix.php?id=41213&r=trysnapshot60
Fixed in CVS: http://bugs.php.net/fix.php?id=41213&r=fixedcvs
Fixed in release:
http://bugs.php.net/fix.php?id=41213&r=alreadyfixed
Need backtrace: http://bugs.php.net/fix.php?id=41213&r=needtrace
Need Reproduce Script: http://bugs.php.net/fix.php?id=41213&r=needscript
Try newer version: http://bugs.php.net/fix.php?id=41213&r=oldversion
Not developer issue: http://bugs.php.net/fix.php?id=41213&r=support
Expected behavior: http://bugs.php.net/fix.php?id=41213&r=notwrong
Not enough info:
http://bugs.php.net/fix.php?id=41213&r=notenoughinfo
Submitted twice:
http://bugs.php.net/fix.php?id=41213&r=submittedtwice
register_globals: http://bugs.php.net/fix.php?id=41213&r=globals
PHP 3 support discontinued: http://bugs.php.net/fix.php?id=41213&r=php3
Daylight Savings: http://bugs.php.net/fix.php?id=41213&r=dst
IIS Stability: http://bugs.php.net/fix.php?id=41213&r=isapi
Install GNU Sed: http://bugs.php.net/fix.php?id=41213&r=gnused
Floating point limitations: http://bugs.php.net/fix.php?id=41213&r=float
No Zend Extensions: http://bugs.php.net/fix.php?id=41213&r=nozend
MySQL Configuration Error: http://bugs.php.net/fix.php?id=41213&r=mysqlcfg
