php.net |  support |  documentation |  report a bug |  advanced search |  search howto |  statistics |  random bug |  login
Bug #10313 ROUND inconsistency
Submitted: 2001-04-12 22:20 UTC Modified: 2001-04-13 14:35 UTC
From: faxguy at deanox dot com Assigned:
Status: Closed Package: *Math Functions
PHP Version: 4.0.4pl1 OS: RedHat Linux 7.0
Private report: No CVE-ID: None
View Add Comment Developer Edit
Welcome! If you don't have a Git account, you can't do anything here.
You can add a comment by following this link or if you reported this bug, you can edit this bug over here.
(description)
Block user comment
Status: Assign to:
Package:
Bug Type:
Summary:
From: faxguy at deanox dot com
New email:
PHP Version: OS:

 

 [2001-04-12 22:20 UTC] faxguy at deanox dot com
Using MySQL 3.23.32 on RedHat Linux 7.0...

MySQL's ROUND function rounds 5 up when the preceding digit is odd and down when the preceding digit is even.

mysql> select round(1.5);
+------------+
| round(1.5) |
+------------+
|          2 |
+------------+
1 row in set (0.00 sec)

mysql> select round(2.5);
+------------+
| round(2.5) |
+------------+
|          2 |
+------------+
1 row in set (0.00 sec)

I think that this is technically the correct behavior, scientifically, anyway.  However, this is not the common "lay-man's" method of rounding, which is to always round 5 up, as exhibited by PHP-4.0.4pl1...

	<? echo round(1.5); ?>
	<br>
	<? echo round(2.5); ?>

Apache 1.3.14 output for this is:

	2
	3

This discrepancy causes a difficulty in programming PHP and MySQL together, for example, because all of the rounding must be done in either PHP or MySQL but not both partially unless you want conflicting data.

I would like to see MySQL ROUND() syntax expand to be ROUND(X,D,M) where optional M value indicates the method of rounding, the default being the current method.

I would also like to see PHP round() syntax expand to be 
	double round (double val [, int precision] [, char method])
where the optional method value indicates the method of rounding, the default being the current method.

Thanks.

Lee Howard

Patches

Add a Patch

Pull Requests

Add a Pull Request

History

AllCommentsChangesGit/SVN commitsRelated reports
 [2001-04-13 14:35 UTC] derick@php.net
This isn't a bug. PHP uses the underlying C library to round, and all known C library's do this the same.
Actually, you are reporting a bug for MySQL, so please ask on there bug list for this.
 [2004-09-06 01:35 UTC] tivnet at mail dot com
The problem still exists - September 2004, latest PHP4 and MySql 4.0
 [2004-09-06 01:53 UTC] tivnet at mail dot com
The quick workaround seems to be using TRUNCATE in MySQL:
TRUNCATE( 38.50 + 0.5, 0 ) = 39
while
ROUND( 38.50, 0 ) = 38

TIV.NET
http://tiv.net/
 
PHP Copyright © 2001-2022 The PHP Group
All rights reserved.
Last updated: Sat Aug 13 18:05:44 2022 UTC