PHP: rfc:json_numeric_as_string

This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.
====== PHP RFC: JSON numeric as string ======
  * Version: 0.1
  * Date: 2015-05-24
  * Author: Jakub Zelenka <bukka@php.net>, Pasindu De Silva <pasindu@php.net>
  * Status: Declined
  * First Published at: http://wiki.php.net/rfc/json_numeric_as_string

===== Introduction =====
JSON is a data format that is often used for data exchange between different platforms. These platforms can have different number representation which might lead to problems like type inconsistency or precision loss.

===== Proposal =====
The proposal introduces new options for dealing with the number conversion problem by converting data to string.

==== Float to string conversion ====
The first option called ''JSON_FLOAT_AS_STRING'' converts all float values to string.

=== Decoding ===
The idea is to convert all float values to string when decoding JSON string. That prevents of precision loss.

== Example ==
<code php>
$data = json_decode('[1.23343224234, 1.34]', true, 512, JSON_FLOAT_AS_STRING);
var_dump($data);
</code>

outputs

<code>
array(2) {
  [0] =>
  string(13) "1.23343224234"
  [1] =>
  string(4) "1.34"
}
</code>

== Use case ==

The use case is preventing precision loss. Currently the float precision is always lost due to C double conversion from string. This is even bigger problem if the user operates with very large numbers.

=== Encoding ===
The idea is to convert all float values to string when encoding PHP value.

== Example ==
<code php>
ini_set('precision', 12);
echo json_encode(arrray("a" => 1.23343224234, JSON_FLOAT_AS_STRING);
</code>

outputs

<code>
{"a":"1.23343224234"}
</code>

== Use case ==

This might be useful when data are exported and then parsed by a parser that can't prevent of precision loss. That might be useful especially for platforms using C float type.

==== Integer to string conversion ====
The second option called ''JSON_INT_AS_STRING'' converts all int values to string.

=== Decoding ===
The idea is to convert all int values to string when decoding JSON string.

== Example ==
<code php>
$data = json_decode('[23343224234, 34]', true, 512, JSON_INT_AS_STRING);
var_dump($data);
</code>

will output:
<code>
array(2) {
  [0] =>
  string(11) "23343224234"
  [1] =>
  string(2) "34"
}
</code>

== Use case ==

This decoding option might be useful when type consistency is required. The problem with precision is already resolved by ''JSON_BIGINT_AS_STRING''. However when the numbers are on the edge of ''INT_MAX'', then the result is combination of strings and integers.

=== Encoding ===
The idea is to convert all int values to string when encoding PHP value.

== Example ==
<code php>
echo json_encode(array( "a"=>123343224234), JSON_INT_AS_STRING);
</code>

will output

<code>
{"a":"123343224234"}
</code>

== Use case ==

This encoding options might be useful when exporting integers greater than ''1 << 31'' from 64bit platforms to 32bit platforms and the target JSON parser cannot handle integer overflow.

===== Backward Incompatible Changes =====
The code that defines ''JSON_FLOAT_AS_STRING'' and/or ''JSON_INT_AS_STRING'' will be broken. However the constants have ''JSON_'' prefix so their usage is not recommended and it should be relatively safe addition.

===== Proposed PHP Version(s) =====
The proposed versions will be one of the voting options as some might consider it as not a self-contained feature.

There will be choice of 3 PHP version.
  - 5.6.next : this voting option considers the feature/bug as a self-contained small addition. The precedence for this is an addition of ''JSON_PRESERVE_ZERO_FRACTION'' that was added in 5.6 cycle.
  - 7.0: this voting option considers the feature/bug as a self-contained but it does not consider feature important for 5.6. It will be up to Release Manager to decide whether to merge it to 7.0.0 or 7.0.1.
  - 7.1: this option will consider the feature/bug as a non self-contained addition

===== New Constants =====
=== JSON_FLOAT_AS_STRING ===
  * json_decode - all float values are decoded as string
  * json_encode - all float values are encoded as string

=== JSON_INT_AS_STRING ===
  * json_decode - all int values are decoded as string
  * json_encode - all int values are encoded as string


===== Drawbacks =====

It is important to note that the number of JSON options is limited to 31 values. There is still space for adding new ones as currently 11 options are used and the future ones can be duplicated for decoding and encoding. However any new addition constant should be properly considered.

In addition, this proposal is not flexible as it has influence on all values of the affected type. That might be unwanted behavior especially for ''JSON_INT_AS_STRING''. The only supported resulted type is a string which is another inflexibility. 


===== Future replacement =====

As noted in the Drawbacks section, this proposal is not flexible. There could be a better solution. That solution could be implementation of Json Schema that would address all drawbacks. However its introduction is only possible in the next minor version and the time for the implementation is considerably bigger.


===== Unaffected PHP Functionality =====
This RFC is related only to JSON extension.

===== Voting =====

50%+1 majority (see [[voting]]) for all votings. 

It started on 2015-06-09 at 20:00 UTC and ended on 2015-06-16 at 20:00 UTC. 

==== JSON_FLOAT_TO_STRING for decoding ====

<doodle title="Include JSON_FLOAT_TO_STRING for decoding?" auth="bukka" voteType="single" closed="true">
   * Yes
   * No
</doodle>

==== JSON_FLOAT_TO_STRING for encoding ====

<doodle title="Include JSON_FLOAT_TO_STRING for encoding?" auth="bukka" voteType="single" closed="true">
   * Yes
   * No
</doodle>

==== JSON_INT_TO_STRING for decoding ====

<doodle title="Include JSON_INT_TO_STRING for decoding?" auth="bukka" voteType="single" closed="true">
   * Yes
   * No
</doodle>

==== JSON_INT_TO_STRING for encoding ====

<doodle title="Include JSON_INT_TO_STRING for encoding?" auth="bukka" voteType="single" closed="true">
   * Yes
   * No
</doodle>

==== PHP version ====

This option applies only if one of the above votes has 50%+1 votes

<doodle title="PHP version used for the included constant" auth="bukka" voteType="single" closed="true">
   * PHP 5.6
   * PHP 7.0
   * PHP 7.1
</doodle>

===== Patches and Tests =====
The patch is really simple and will be implemented by the author of this RFC if accepted.

===== References =====
  * Bug for float precision loss: https://bugs.php.net/bug.php?id=68456
  * Initial discussion about introduction ''JSON_FLOAT_TO_STRING'': http://bit.ly/1D2ZyAR
  * JSON Schema spec: http://json-schema.org/
Page Tools
