#36008 [Com]: incorrect round() & number_format() result

ID: 36008 Comment by: me at nospam dot com Reported By: adi at rogers dot com Status: No Feedback Bug Type: Math related Operating System: win32 only PHP Version: 5CVS-2006-06-14 New Comment: I don't have a simpler test case, but in doing more testing, I found that the rounding apparently just doesn't work. When you print out a number that was rounded, it will appear correctly, but when you try to do math functions with other similar numbers (ie 6.08 - 6.08), I will get a remainder of like 2.039283e-16. However, setting the type to each variable as a string made it work correctly. Previous Comments: ------------------------------------------------------------------------ [2007-01-15 01:00:00] php-bugs at lists dot php dot net No feedback was provided for this bug for over a week, so it is being suspended automatically. If you are able to provide the information that was originally requested, please do so and change the status of the bug back to "Open". ------------------------------------------------------------------------ [2007-01-09 02:56:14] terrychangsharp at gmail dot com I tested the code on PC + FreeBSD 6.1 + Apache 2.2.3 + PHP 5.2.0 and get the same results. Actually, the seemingly coincident numbers $num and $num_same_thing are in fact not the same thing: $num - $num_same_thing yields -1.7763568394003E-015, not zero, so $num is smaller than 14.375 and round($num) is 14.37, not 14.38. Thus this "bug" is more like a floating point error thing, not a real bug. ------------------------------------------------------------------------ [2007-01-07 04:07:29] iliaa@php.net Please try using this CVS snapshot: http://snaps.php.net/php5.2-latest.tar.gz For Windows: http://snaps.php.net/win32/php5.2-win32-latest.zip ------------------------------------------------------------------------ [2006-10-31 00:39:37] adi at rogers dot com Aww well it's too late for me to bug it for Windows Vista as we've entered Release Candidate 2 :( I'll test this again on IIS7 with the final version of Vista... ------------------------------------------------------------------------ [2006-10-30 13:30:58] dave at koales dot co dot uk I think this is a Windows vs others thing. I have the same rounding error using PHP 5.0.5 on Windows XP SP2. The same problem does not exist on my webhost, who use PHP 4.3.9 and Redhat Linux (need any more detail). The code I used was: echo "Correct VAT = " . round( 0.525, 2 ) . "\r\n"; echo "Wrong VAT = " . round( 3 * ( 17.5 / 100.0 ), 2 ) . "\r\n"; Outputs 0.53 for each on webhost (under Linux) and 0.52 for the second test under Windows (0.53 for the first test). I've also had very bizarre rounding errors with MySQL. The rounding error came and went depending on how the calculation was constructed! ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at http://bugs.php.net/36008 -- Edit this bug report at http://bugs.php.net/?id=36008&edit=1