Bug #74925 [Opn->Nab]: Mismatching floating values

Edit report at https://bugs.php.net/bug.php?id=74925&edit=1 ID: 74925 Updated by: krakjoe@php.net Reported by: tuepp at gmx dot de Summary: Mismatching floating values -Status: Open +Status: Not a bug Type: Bug Package: PHP Language Specification Operating System: Windows PHP Version: 7.0.21 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: ------------------------------------------------------------------------ [2017-07-14 14:42:09] tuepp at gmx dot de Description: ------------ Floating number comparison fails for numbers that have to be rounded internal. This bug may be over 10 years old. I've reported it 5 years ago and it is still not fixed. Now I have an example with one instead of 3 lines of code what might be more shoking. I've documented this bug in my final exam 6 years ago and it feeled like I got some extra points for it - so thank you. But now it's really time to fix it! I'm not sure if I'll report it a third time in another 5 years... So go, get it! Test script: --------------- <?php echo (54.83 + 0.01 == 54.84) ? 'ok' : 'fail'; //fail echo "<br>\n"; echo ((3 * 202.3) == 606.9) ? 'ok' : 'fail'; //fail echo "<br>\n"; for($v = -1; $v < 0; $v += 0.2){ echo "$v; "; // -1; -0.8; -0.6; -0.4; -0.2; -5.5511151231258E-17; } Expected result: ---------------- ok ok -1; -0.8; -0.6; -0.4; -0.2 Actual result: -------------- fail fail -1; -0.8; -0.6; -0.4; -0.2; -5.5511151231258E-17; ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=74925&edit=1