Bug #74665 [Com]: Floats sum return quirk

Edit report at https://bugs.php.net/bug.php?id=74665&edit=1 ID: 74665 Comment by: tomasz dot kane at gmail dot com Reported by: tomasz dot kane at gmail dot com Summary: Floats sum return quirk Status: Not a bug Type: Bug Package: Variables related Operating System: Kubuntu PHP Version: 7.1.5 Block user comment: N Private report: N New Comment: Oh, my bad, if the result should be 1 then I can expect 0,999~ In this case more reasonable is something like 0,000000000001 (for humans ;-)) I feel convinced. Previous Comments: ------------------------------------------------------------------------ [2017-05-28 09:19:15] a at b dot c dot de What's wrong with 2.2204460492503E-16? That's 2**-52; about as close to zero as 64-bit IEEE754 floating point can get without actually being zero. Why you'd expect 0.99999~ (or about roughly 1) instead is baffling. ------------------------------------------------------------------------ [2017-05-27 20:12:28] tomasz dot kane at gmail dot com Thanks for answer, I'll use bc but... I can accept result like: 0.99999~ but 2.2204460492503E-16 ?! Madness :-) ------------------------------------------------------------------------ [2017-05-27 18:18:56] jhdxr@php.net you may use [bc math](http://jp2.php.net/manual/en/ref.bc.php) to get the precise result. ------------------------------------------------------------------------ [2017-05-27 18:16:19] jhdxr@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. ------------------------------------------------------------------------ [2017-05-27 17:52:58] tomasz dot kane at gmail dot com Description: ------------ I'm just calculate array values sum. BTW I know about Floating point precision, but this result... Test script: --------------- $foo = [2.45, -1.05, -1.40]; echo array_sum($foo); // 2.2204460492503E-16 // same result when use foreach $sum += $item Expected result: ---------------- 0 Actual result: -------------- 2.2204460492503E-16 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=74665&edit=1