Edit report at https://bugs.php.net/bug.php?id=50224&edit=1
ID: 50224
Comment by: josh dot adell at gmail dot com
Reported by: christian dot lawrence at calorieking dot com
Summary: json_encode() does not always encode a float as a
float
Status: Not a bug
Type: Bug
Package: JSON related
PHP Version: 5.2SVN-2009-11-19 (snap)
Block user comment: N
Private report: N
New Comment:
This is still an issue, specifically when JSON encoding for talking to APIs that
don't allow mixed type arrays.
For instance, json_encode(array(1.2, 2.3)) properly encodes to "[1.2, 2.3]"
But, json_encode(array(1.0, 2.3)) encodes to "[1, 2.3]" which fails if the
receiving end does not allow mixed-type arrays.
Any chance on this ever being fixed?
PHP Version: 5.3.10
Previous Comments:
------------------------------------------------------------------------
[2009-11-20 10:39:53] christian dot lawrence at calorieking dot com
And there lines the problem - there is no way to express the fractional part if json_encode() does
not even deal with it in the first place.
An integer and an integer represented as a floating point number are not the same thing because they
have different types, as follows:
<?php
$a = 12;
var_dump($a); //int(12)
$b = 12.0; // This has a fractional part, hence it is a floating point number and not an
integer
var_dump($b); //float(12)
var_dump($a === $b); //bool(false)
?>
Numerically they have the same value, but we all know this to be true:
<?php
var_dump($a == $b); //bool(true)
?>
There is always a fractional part of any integer when it is represented as a floating point number.
It is implied and can, simply, be expressed by appending a ".0" to the integer part.
There is nothing in the JSON encoding rules on http://www.json.org/ which disallows this (see "int frac"
form for specifics).
Decoding a valid and legitimate encoding of an integer when it is represented as a floating point
number gives the correct PHP floating point type:
<?php
var_dump(json_decode("12.0")); //float(12)
?>
Decoding an integer-encoded stream also gives the correct PHP integer type:
<?php
var_dump(json_decode("12")); //int(12)
?>
I fail to see how my bug report is bogus when json_encode() is unable to produce a perfectly valid
and legitimate encoding yet json_decode() is capable of doing the right thing.
Surely, the json_encode() implementation must be identifying the data type being encoded, presumably
it is using equivalents for is_object() and is_array(). Why not use equivalents for is_int() or
is_float() as well?
A reliable data interchange format should not purport to do any type-casting from the primitive
types it was provided for encoding. ie: If you encode a float then you should expect to decode a
float. As far as I am concerned json_encode() is un-reliable and fails to encode my float, which I
have confirmed in my results.
I humbly ask that you reconsider your position.
------------------------------------------------------------------------
[2009-11-19 15:12:56] jani@php.net
Yes, IF you were passing fractional part. But you're not. See the output of var_dump($f) in
your results..
------------------------------------------------------------------------
[2009-11-19 09:14:05] christian dot lawrence at calorieking dot com
Take a look at the format for "number" at http://www.json.org/ and observe the form for a "int
frac". This clearly indicates that there is support for representing a floating point number,
even integer floats.
The json_encode() function clearly supports encoding of floating point numbers. json_decode() is
capable of deserialising "12.0" as a integer floating point number.
If you encode a floating point number, then one should expect to decode a floating point number.
If json_encode()/json_decode() is to be used as a serious and reliable data exchange format, then
there should be no loss or conversion of primitive type information.
Please re-consider.
------------------------------------------------------------------------
[2009-11-19 08:51:56] jani@php.net
There's is just "number" type in JSON for numbers. And as such, this is working just
like it should and PHP tries it's best at guessing what type the numbers might be.
------------------------------------------------------------------------
[2009-11-19 05:45:10] christian dot lawrence at calorieking dot com
Description:
------------
json_encode()-ing an integer when it is represented as floating point number results in a change of
type when json_decode() decodes the output.
Examples of such floating point numbers are: -123.0, -1.0, 0.0, 1.0, 123.0
Reproduce code:
---------------
<?php
function jsonRoundTrip($f) {
$e = json_encode($f);
$d = json_decode($e);
var_dump($f, $e, $d);
echo "\n";
}
jsonRoundTrip(12.3); // This is a float
jsonRoundTrip(12); // This is an integer
jsonRoundTrip(12.0); // This is an integer represented as a float
jsonRoundTrip(0.0); // This is an integer represented as a float
?>
Expected result:
----------------
float(12.3)
string(4) "12.3"
float(12.3)
int(12)
string(2) "12"
int(12)
float(12)
string(4) "12.0"
float(12)
float(0)
string(3) "0.0"
float(0)
Actual result:
--------------
float(12.3)
string(4) "12.3"
float(12.3)
int(12)
string(2) "12"
int(12)
float(12)
string(2) "12"
int(12)
float(0)
string(1) "0"
int(0)
------------------------------------------------------------------------
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Edit this bug report at https://bugs.php.net/bug.php?id=50224&edit=1