Bug #70598 [Nab]: Comparison fails for array values of type float

Edit report at https://bugs.php.net/bug.php?id=70598&edit=1 ID: 70598 User updated by: mv dot pestov at gmail dot com Reported by: mv dot pestov at gmail dot com Summary: Comparison fails for array values of type float Status: Not a bug Type: Bug Package: Arrays related Operating System: Debian Wheezy PHP Version: 5.6.13 Block user comment: N Private report: N New Comment: Thank you very much for your detailed explanation. I'll read the link you have provided by this subject. Previous Comments: ------------------------------------------------------------------------ [2015-09-28 20:19:06] rasmus@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. $i += 0.2 is not going to be precise. Floating point doesn't work that way. ------------------------------------------------------------------------ [2015-09-28 11:27:11] mv dot pestov at gmail dot com Description: ------------ When populating an array with values of type float from loop and then the comparison (==) fails. If create an array using array() this bug not reproduces. Test script: --------------- <?php $array = array(); for($i = 1.4; $i <= 2; $i += 0.2) { $array[] = $i; } if($array[3] == 2) echo 'true'; else echo 'false'; Expected result: ---------------- true Actual result: -------------- false ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=70598&edit=1