Bug #79338 [Com]: fmod() not calculating properly

Edit report at https://bugs.php.net/bug.php?id=79338&edit=1 ID: 79338 Comment by: rico dot humme at gmail dot com Reported by: ziggi at ziggi dot pl Summary: fmod() not calculating properly Status: Not a bug Type: Bug Package: *Math Functions Operating System: Windows PHP Version: 7.4.3 Block user comment: N Private report: N New Comment: As of today this has not yet been resolved, sadly for($i = 1; $i <= 10; $i++) { $dividend = round($i * 3.2, 2); echo "fmod($dividend, 3.2) > " . fmod($dividend, 3.2)."\n"; } Output: fmod(3.2, 3.2) > 0 fmod(6.4, 3.2) > 0 fmod(9.6, 3.2) > 3.2 fmod(12.8, 3.2) > 0 fmod(16, 3.2) > 3.2 fmod(19.2, 3.2) > 3.2 fmod(22.4, 3.2) > 3.2 fmod(25.6, 3.2) > 0 fmod(28.8, 3.2) > 3.2 fmod(32, 3.2) > 3.2 Previous Comments: ------------------------------------------------------------------------ [2020-03-03 17:43:23] derick@php.net PERL: $ perl -e 'use POSIX (); print POSIX::fmod(75.6, 25.2);' 25.2 ------------------------------------------------------------------------ [2020-03-03 17:41:01] ziggi at ziggi dot pl OK, Not really good at all but obviously "obvious"... >> Get off my lawn. I do. Do not get upset so easy, man! Thank you for your time, anyway. ------------------------------------------------------------------------ [2020-03-03 17:34:34] nikic@php.net > import math > print(math.fmod(75.6, 25.2)) 25.199999999999996 Surprising absolute nobody, Python returns the same result. Obviously. Get off my lawn. ------------------------------------------------------------------------ [2020-03-03 17:09:45] ziggi at ziggi dot pl Well, My conclusion: PHP: echo 2.0 * 2.0; outcome: 5.0 OMG! Why 2 * 2 is 5 in PHP??? Answer from PHP team: Because we use shitty C library with twisted precision so 2 * 2 is often 5. Enjoy or use Python. ------------------------------------------------------------------------ [2020-03-03 11:38:55] cmb@php.net Also note: <?php $num = 75.6; $denom = 25.2; $res = fmod($num, $denom); var_dump($res === $denom); // bool(false) ?> Further reading: <http://www.floating-point-gui.de/> ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at https://bugs.php.net/bug.php?id=79338 -- Edit this bug report at https://bugs.php.net/bug.php?id=79338&edit=1