Bug #51233 [Bgs]: Wrong results with float arithmetics

Edit report at http://bugs.php.net/bug.php?id=51233&edit=1 ID: 51233 User updated by: daniel dot seif at castex dot de Reported by: daniel dot seif at castex dot de Summary: Wrong results with float arithmetics Status: Bogus Type: Bug Package: Scripting Engine problem Operating System: Multiple PHP Version: 5.3.2 New Comment: Thank you for the quick reply. The string representation is not the problem here, though. We are calculating with monetary data and converting from one currency to another. Imagine a two products, worth 138.00 and 0.95 with the need to keep only 2 decimal digits: $totalPrice = floor((138.00 + 0.95) * 100) / 100; The result should be 138.95, but PHP returns 138.94 ... I consider this to be a problem on a worse level than just 'bogus' Best Regards Previous Comments: ------------------------------------------------------------------------ [2010-03-08 12:12:03] johannes@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. ------------------------------------------------------------------------ [2010-03-08 11:57:15] daniel dot seif at castex dot de Description: ------------ When calculating with and rounding float values, the result of the calculation is wrong. This bug seems to affect multiple versions of php. I have tested it with PHP 5.3.2 (Fedora 12), PHP 5.2.6 (Red Hat), PHP 5.3.0 (Windows XP). Test script: --------------- echo floor(138.95 * 100), "\n"; echo floor(141.95 * 100), "\n"; echo floor(142.95 * 100), "\n"; echo intval(142.95 * 100), "\n"; echo (int)(138.95 * 100); Expected result: ---------------- 13895 14195 14295 14295 13895 Actual result: -------------- 13894 14194 14294 14294 13894 ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/bug.php?id=51233&edit=1