Bug #62845 [Com]: round returns -0

Edit report at https://bugs.php.net/bug.php?id=62845&edit=1 ID: 62845 Comment by: hanskrentel at yahoo dot de Reported by: bradley dot lee80 at googlemail dot com Summary: round returns -0 Status: Not a bug Type: Bug Package: Math related Operating System: Linux (Ubuntu) PHP Version: 5.3.16 Block user comment: N Private report: N New Comment: If the -0 is expected, then this indeed was wrong in some PHP versions: <?php $value = -2.2204460492503E-16; $round = round($value, 4); var_dump($round); Output for 4.3.0 - 5.2.0, 5.3.4 - 5.3.6, hhvm-3.0.1 - 3.3.1 float(0) Output for 5.2.1 - 5.3.3, 5.3.7 - 5.6.3, php7@20140507 - 20141101 float(-0) see http://3v4l.org/OcEso Previous Comments: ------------------------------------------------------------------------ [2012-08-17 12:24:48] rasmus@php.net Computers use a standard described in IEEE-754 to handle floating point values. IEEE-754 uses -0 to describe values that approach 0 from a negative value. You will see the same thing in any language that uses the computer's built-in floating point mechanism. C, Python, Ruby, Perl, etc. For example in Python: >>> round(-0.1) -0.0 You can read more about it at: http://en.wikipedia.org/wiki/Signed_zero ------------------------------------------------------------------------ [2012-08-17 12:22:16] nikic@php.net Could you elaborate on why this would not be the expected behavior? Also zero and negative zero are defined to compare equal, so I'm not sure whether this makes any difference in practice. ------------------------------------------------------------------------ [2012-08-17 09:30:23] bradley dot lee80 at googlemail dot com Description: ------------ --- From manual page: http://www.php.net/function.round#refsect1-function.round-description --- The round function returns -0 if the value is a negative value that should round to 0 Test script: --------------- <?php echo round(-0.1); ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=62845&edit=1