PHP RFC: JSON Preserve Fractional Part

• Version: 0.1
• Date: 2014-12-25
• Author: Juan Basso, jrbasso@gmail.com
• Status: Draft
• First Published at: http://wiki.php.net/rfc/json_preserve_fractional_part

This RFC suggests adding a new option to json_encode function to keep the fractional part on float values.

Currently encoding float values like 10.0 to json encodes it as 10, it means that using json_decode function it decodes as integer. The new flag allows the encode to keep the float number encoding 10.0 to 10.0 in JSON.

// Currently
var_dump(json_decode(json_encode((float)10))); // Output int(10)
 
// Proposed
var_dump(json_decode(json_encode((float)10, JSON_PRESERVE_FRACTIONAL_PART))); // Output double(10)

This RFC introduces no BC breaks.

The next PHP 5.x.y.

No impact.

No impact.

No impact.

- JSON_PRESERVE_FRACTIONAL_PART: Preserve the fraction part of float numbers with zero as decimal part.

The implementation of this RFC changed how to encode float numbers and it affected the performance of the json_encode even when not using the new flag.

The table below shows the performance of the code below (PS: not using the new flag):

$data = array_fill(0, 1000, 1.1);
$iterations = 10000;
 
while ($iterations-- > 0) {
        json_encode($data);
}

+-------------------------------------------------------------------------------------+
| Number | With changes | Elapsed time                   | Peak Memory (real = false) |
+-------------------------------------------------------------------------------------+
| 1.0    | No           | 2.6276361942291                | 331 688                    |
| 1.0    | Yes          | 1.9471561908722 (25.9% faster) | 331 496                    |
| 1.1    | No           | 2.672217130661                 | 335 616                    |
| 1.1    | Yes          | 2.0137410163879 (24.6% faster) | 335 424                    |
+-------------------------------------------------------------------------------------+

PS: Tests executed from Mac OS X 10.10.1 using CPU 2.3 GHz Intel Core i7 and 16GB of RAM.

PS 2: The changes made on this RFC doesn't affect the performance of other value types.

Define if this behavior should be enabled by default in PHP 7.

This RFC requires a 50%+1 majority.

Currently implemented on https://github.com/php/php-src/pull/642

None so far.