rfc:precise_float_value
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| rfc:precise_float_value [2015/09/25 00:05] – yohgaki | rfc:precise_float_value [2016/05/30 16:27] – Update RFC and add me as an co-author bukka | ||
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| ====== PHP RFC: More precise float value handling ====== | ====== PHP RFC: More precise float value handling ====== | ||
| - | * Version: | + | * Version: |
| * Date: 2015-07-30 | * Date: 2015-07-30 | ||
| - | * Author: Yasuo Ohgaki < | + | * Author: Yasuo Ohgaki < |
| * Status: Under Discussion | * Status: Under Discussion | ||
| * First Published at: http:// | * First Published at: http:// | ||
| Line 8: | Line 9: | ||
| ===== Introduction ===== | ===== Introduction ===== | ||
| - | This RFC is based on float like JSON numeric | + | This RFC is based on the discussion |
| - | JSON is used to exchange data between systems. Although [[https:// | + | JSON is used to exchange data between systems. Although [[https:// |
| - | Currently, json_encode() uses EG(precision) which is 14. IEEE 754 double supports | + | Currently, json_encode() uses EG(precision) which is set to 14. That means that 14 digits max are used for displaying (printing) the number. IEEE 754 double supports |
| <code php> | <code php> | ||
| Line 40: | Line 41: | ||
| </ | </ | ||
| - | PHP's float type stores " | + | PHP's float type stores " |
| Current PHP outputs meaningless values for oversized EG(precision)/ | Current PHP outputs meaningless values for oversized EG(precision)/ | ||
| Line 57: | Line 58: | ||
| float(0.12345678901234567736988623209981597028672695159912109375) | float(0.12345678901234567736988623209981597028672695159912109375) | ||
| </ | </ | ||
| + | |||
| + | That is caused by used mode for double to string conversion. | ||
| ===== Proposal ===== | ===== Proposal ===== | ||
| - | * PHP 7.1: Introduce | + | This RFC proposes to introduce |
| - | + | ||
| - | Since JSON is used extensively for web apps, we may have JSON specific INI setting for better compatibility and ease of use. | + | |
| - | + | ||
| - | * PHP 7.1: Add JSON_G(json_precision) - Add JSON module specific precision INI setting. | + | |
| - | + | ||
| - | PHP 5.6/ | + | |
| - | + | ||
| - | * PHP 5.6/7.0: Make json_encode() uses PG(serialize_precision). | + | |
| + | Since JSON is used extensively for web apps, we may have JSON specific INI setting for better compatibility and ease of use. It means to add JSON_G(json.precision) which will be used for JSON module specific precision INI setting. | ||
| Followings are sample codes and outputs of the proposed patch. | Followings are sample codes and outputs of the proposed patch. | ||
| Line 123: | Line 119: | ||
| ===== Backward Incompatible Changes ===== | ===== Backward Incompatible Changes ===== | ||
| - | PHP 7.0 will have 0 mode as the default. var_export()/ | + | Setting |
| - | FYI: Existing | + | The BC break could happen only if someone would rely on exact output but that shouldn' |
| None when old INI value is used. | None when old INI value is used. | ||
| Line 131: | Line 127: | ||
| ===== Proposed PHP Version(s) ===== | ===== Proposed PHP Version(s) ===== | ||
| - | * PHP 7.1.0 - EG(precision)/ | + | * PHP 7.1 |
| - | * PHP 5.6.x/7.0.0 - JSON uses PG(serialize_precision) for float precision. | + | |
| ===== RFC Impact ===== | ===== RFC Impact ===== | ||
| Line 143: | Line 138: | ||
| Standard module | Standard module | ||
| - | * serialize(), | + | * serialize(), |
| JSON | JSON | ||
| - | * json_encode() - PHP7.1: | + | * json_encode() - Use ini selected from the vote result |
| Line 164: | Line 159: | ||
| * php.ini-production values : 14 Unmodified | * php.ini-production values : 14 Unmodified | ||
| - | serialize_precision(PHP5.6) | + | serialize_precision |
| - | * hardcoded default values : 17 Unmodified | + | |
| - | * php.ini-development values : 17 Unmodified | + | |
| - | * php.ini-production values : 17 Unmodified | + | |
| - | + | ||
| - | serialize_precision(PHP7) | + | |
| * hardcoded default values : -1 | * hardcoded default values : -1 | ||
| * php.ini-development values : -1 | * php.ini-development values : -1 | ||
| * php.ini-production values : -1 | * php.ini-production values : -1 | ||
| - | json_precision(NEW - PHP7 only) | + | json.precision |
| * hardcoded default values : -1 | * hardcoded default values : -1 | ||
| * php.ini-development values : -1 | * php.ini-development values : -1 | ||
| Line 190: | Line 180: | ||
| ===== Future Scope ===== | ===== Future Scope ===== | ||
| - | |||
| - | * Remove PG(serialize_precision) setting. If we are going to remove PG(serialize_precision) in the future, we may be better to have JSON_G(json_precision) as one may need specific precision for JSON data. | ||
| WDDX | WDDX | ||
| Line 204: | Line 192: | ||
| Requires a 50%+1 majority | Requires a 50%+1 majority | ||
| - | Please choose Yes/No for 0 mode EG(precision)/ | + | There will be two votings |
| - | + | ||
| - | <doodle title=" | + | |
| - | * Yes | + | |
| - | * No | + | |
| - | </ | + | |
| - | + | ||
| - | . | + | |
| - | + | ||
| - | Please choose your preference whether JSON module should use PG(serialize_precision) or new JSON_G(json_precision). i.e. JSON module has its own precision setting or not. | + | |
| - | + | ||
| - | <doodle title=" | + | |
| - | * Yes | + | |
| - | * No | + | |
| - | </ | + | |
| - | + | ||
| - | . | + | |
| - | + | ||
| - | Please choose if PHP 5.6's JSON should use PG(serialize_precision) or EG(precision). Currently it uses EG(precision). | + | |
| - | + | ||
| - | <doodle title=" | + | |
| - | * Yes | + | |
| - | * No | + | |
| - | </ | + | |
| - | + | ||
| - | Please choose if PHP 7.0's JSON should use PG(serialize_precision) or EG(precision). Currently it uses EG(precision). | + | |
| - | + | ||
| - | <doodle title=" | + | |
| - | * Yes | + | |
| - | * No | + | |
| - | </ | + | |
| + | * whether to introduce mode 0 as default | ||
| + | * what precision ini should be used for json (precision, serialize_precision, | ||
| ===== Patches and Tests ===== | ===== Patches and Tests ===== | ||
| Line 250: | Line 209: | ||
| ===== References ===== | ===== References ===== | ||
| - | https:// | + | * https:// |
| + | * https:// | ||
| + | * http:// | ||
| ===== Rejected Features ===== | ===== Rejected Features ===== | ||
| Keep this updated with features that were discussed on the mail lists. | Keep this updated with features that were discussed on the mail lists. | ||
rfc/precise_float_value.txt · Last modified: 2017/09/22 13:28 by 127.0.0.1