Bug #68111 [Com]: json_decode introduces floating point precision error
Edit report at https://bugs.php.net/bug.php?id=68111&edit=1
ID: 68111
Comment by: admin at bittylicious dot com
Reported by: ryan at ryanparman dot com
Summary: json_decode introduces floating point precision
error
Status: Not a bug
Type: Bug
Package: JSON related
Operating System: OS X
PHP Version: 5.5.17
Block user comment: N
Private report: N
New Comment:
I've created a partially-related feature request for this to have an option for json_decode to
handle all numbers as strings. If you're never going to use the result as a double internally,
this can be useful.
https://bugs.php.net/bug.php?id=68456
Previous Comments:
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[2014-09-29 17:25:19] ryan at ryanparman dot com
So, I would like to better understand why two versions of PHP give me different results.
----
$ php --version
PHP 5.5.17 (cli) (built: Sep 19 2014 00:50:57)
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2014 Zend Technologies
with Xdebug v2.2.5, Copyright (c) 2002-2014, by Derick Rethans
$ php -i | grep -i precision
precision => 14 => 14
serialize_precision => 17 => 17
----
$ php --version
PHP 5.4.33 (cli) (built: Sep 20 2014 16:20:03)
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.4.0, Copyright (c) 1998-2014 Zend Technologies
with Xdebug v2.2.5, Copyright (c) 2002-2014, by Derick Rethans
$ php -i | grep -i precision
precision => 14 => 14
serialize_precision => 100 => 100
----
Could it be because the serialize_precision value is different?
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[2014-09-29 16:09:18] aharvey@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://www.floating-point-gui.de/
Thank you for your interest in PHP.
It's going to be the same value on both, just with different precision settings controlling the
output.
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[2014-09-27 05:05:07] ryan at ryanparman dot com
This should be filed under JSON-related.
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[2014-09-27 05:00:56] ryan at ryanparman dot com
Description:
------------
When decoding a JSON string with json_decode(), a floating point precision error gets introduced.
Issue identified in PHP 5.5.17, and verified that it does NOT occur in 5.4.33.
Test script:
---------------
$data = json_decode('{"value": 4565.85}');
echo $data->value;
Expected result:
----------------
I expected $data->value to have a value of 4565.85.
Actual result:
--------------
The actual value of $data->value is 4565.8500000000004.
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Edit this bug report at https://bugs.php.net/bug.php?id=68111&edit=1
Thread (5 messages)