Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:87347
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.213.174 as permitted sender)
MIME-Version: 1.0
Sender: jakub.php@gmail.com
In-Reply-To: <CAGa2bXYMffoBdnh_0HmyQv23KZtsb5RWpJqjosKFa0p_66+vaQ@mail.gmail.com>
References: <CAGa2bXYgtZ8PZbmFD5hs2gj7b+MTM8-s1DvK+P5dhCU5y+W6Hw@mail.gmail.com>
	<CAEKnhAGfuy6G92=Ng4bbSOOP-mE2t5_cNXnY0QpgHnu-i4Mfjg@mail.gmail.com>
	<CAGa2bXZY3HvXd0yRaG6g-Ewuya+iLc3dsYtJFMfn9FiAbo27tA@mail.gmail.com>
	<CAAyV7nGdAKLmJG81dnG_cGDDCLduMV3gJta+YgwNp5MJ414OJQ@mail.gmail.com>
	<CAGa2bXaWu5uaa2kRvrmnO-JWsCq-uTeQUCNGvafOqHi4c4D7AA@mail.gmail.com>
	<CAGa2bXYMffoBdnh_0HmyQv23KZtsb5RWpJqjosKFa0p_66+vaQ@mail.gmail.com>
Date: Tue, 28 Jul 2015 19:15:06 +0100
Message-ID: <CAEKnhAEoVNqs6omdZgYHcX1wG3Q9VFvGciptJtr8CZJG92mG_A@mail.gmail.com>
To: Yasuo Ohgaki <yohgaki@ohgaki.net>
Cc: Anthony Ferrara <ircmaxell@gmail.com>, 
	"internals@lists.php.net" <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=001a113f1ef225fbad051bf37304
Subject: Re: [PHP-DEV] json_decode/encode should return full precision values
 by default
From: bukka@php.net (Jakub Zelenka)

--001a113f1ef225fbad051bf37304
Content-Type: text/plain; charset=UTF-8

Hi Yasuo

On Mon, Jul 27, 2015 at 11:17 PM, Yasuo Ohgaki <yohgaki@ohgaki.net> wrote:

>
> Get JSON data from Google maps and store the data using PHP, then
> users lose last 2 digits of fraction part by default. The value is changed
> and wrong. This is definitely a bug.
>
>
I don't really get why you use Google maps as an example. Do you actually
know what's the difference between two distances that differs after
rounding with precision 14?

I just tried it on
http://www.ig.utexas.edu/outreach/googleearth/latlong.html and set

Lat 1: 51.602097123457   ; Long 1:  -0.120667
Lat 2: 51.602097123458   ; Long 2:  -0.120667

The difference is 1.114e-10 km which is 0.0001114 millimetres. Are you
actually serious about that? :)



> We can write
>
> $old = ini_set('precision', 17);
> json_encode($var);
> ini_set('precision', $old);
>

You can set it once in your ini file if you need such precision.


>
> everywhere to workaround this problem.
>
> Question is "Is this the way it should be?".
>
>
I have already said that using precision ini wasn't the best idea. However
json_encode is not the same as serialize and we should not ever change its
output in a bug fixing release. Doing that could cause also other issues as
this is a BC break. Lets imagine that someone set low precision on purpose
just to limit precision and save some space when transferring data . If you
change it, then it's screwed up because it will use different ini. We don't
know what people do in their code and we should not break it. As I said
this is not a bug but we could consider changing that if the RFC proposing
such change passes.

Cheers

Jakub

--001a113f1ef225fbad051bf37304--