#34967 [Opn->Bgs]: $y=1.3+0.1>1.4

ID: 34967 Updated by: tony2001@php.net Reported By: davidyht516 at hotmail dot com -Status: Open +Status: Bogus Bug Type: Math related Operating System: windows xp home PHP Version: 5.0.5 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://docs.sun.com/source/806-3568/ncg_goldberg.html Thank you for your interest in PHP. Previous Comments: ------------------------------------------------------------------------ [2005-10-24 12:53:02] davidyht516 at hotmail dot com Description: ------------ The erro is: 1.3+0.1>1.4 Reproduce code: --------------- $y=1.3+0.1; if($y==1.4){$y-=1.4; echo "yes y-1.4=$y";} else{$y-=1.4; echo "no y-1.4=$y";} Expected result: ---------------- The result of the code should be: yes y-1.4=0 Actual result: -------------- Actual result is: no y-1.4=2.2e-12 It happens only when $y=1.3+0.1; If changing the code to $y=1.2+0.2; then the result is correct. What is going on here? ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=34967&edit=1