#40892 [Bgs]: floating point rounding issue

ID: 40892 User updated by: fizz at beyond dot hjsoft dot com Reported By: fizz at beyond dot hjsoft dot com Status: Bogus Bug Type: Math related Operating System: linux, solaris PHP Version: 5.2.1 New Comment: I very much understand that, my concern was more of a consistency issue between how echo and var_dump does it (which outputs the correct information) and how printf/sprintf does (which gives incorrect output). Previous Comments: ------------------------------------------------------------------------ [2007-03-22 14:23:26] tony2001@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://docs.sun.com/source/806-3568/ncg_goldberg.html Thank you for your interest in PHP. ------------------------------------------------------------------------ [2007-03-22 14:13:24] fizz at beyond dot hjsoft dot com Description: ------------ When printing out a floating point number using printf (or storing it with sprintf, or casting it as an int) it gives an incorrect number. This appears to be due to floating point math being inaccurate. Reproduce code: --------------- <?php $val = 309; for ($x = 0; $x < 950; $x++) $val += 0.001; var_dump($val); echo $val . "\n"; $val = $val * 100; var_dump($val); echo $val . "\n"; printf ("%d\n", $val); echo (int)$val . "\n"; ?> Expected result: ---------------- float(309.95) 309.95 float(30995) 30995 30995 30995 Actual result: -------------- float(309.95) 309.95 float(30995) 30995 30994 30994 ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=40892&edit=1