Bug #72487 [Opn->Nab]: 100 - 99.6 why result = 0.400000001

Edit report at https://bugs.php.net/bug.php?id=72487&edit=1 ID: 72487 Updated by: rasmus@php.net Reported by: wee_weerapat at hotmail dot com Summary: 100 - 99.6 why result = 0.400000001 -Status: Open +Status: Not a bug Type: Bug Package: PHP Language Specification Operating System: Mac & Windows PHP Version: 5.5.37 Block user comment: N Private report: N New Comment: 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. . Previous Comments: ------------------------------------------------------------------------ [2016-06-24 11:37:27] wee_weerapat at hotmail dot com Description: ------------ I'm not sure. 100-99.6 the result will return 0.400000001 and i try many case 100 - 99.96 the result still same 0.040000000000006 There return another position of number Test script: --------------- echo 100-99.6; echo "<br>"; echo 100-99.96; echo "<br>"; echo 1000-999.96; Expected result: ---------------- 0.4 0.04 0.04 Actual result: -------------- 0.40000000000001 0.040000000000006 0.039999999999964 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=72487&edit=1