PHP RFC: json_encode indentation


Programs can serialize data to JSON using the json_encode function. The function is widely used for generating JSON responses or payload over HTTP. Currently, it's not possible to tell json_encode what indentation level (2 spaces, 4 spaces, etc.) should be used when using the JSON_PRETTY_PRINT option. When generating JSON files which can be used/read/edited by users, indentation starts to become a relevant topic.


Introducing a 4th parameter, called indent. The type of the parameter is int and its default value is 4.

By default, an indentation of 4 spaces will be applied, just like the original json_encode behaviour with the JSON_PRETTY_PRINT option.

When the indent parameter is passed a different value, an indentation of N spaces will be applied.

$data = [
    'key' => 4,
    'other_key' => [2]
echo json_encode(['behavior' => 'default'], JSON_PRETTY_PRINT) . PHP_EOL;
echo json_encode($data, JSON_PRETTY_PRINT, 512, 2) . PHP_EOL;
    "behavior": "default"
  "key": 4,
  "other_key": [

Backward Incompatible Changes

The only breaking change this could cause is when programs are already passing a fourth parameter by accident.

Proposed PHP Version(s)

  • next PHP 8.x

Unaffected PHP Functionality

Normal usage (as opposed to what is described in BIC) of the json_encode function will not be affected, as the default of 4 spaces will still be in effect.

Patches and Tests

Tests are written with the RFC


Voting opened on 2022-07-04 and closes on 2022-07-18.

Add support for changing the JSON indentation amount?
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aaronjunker (aaronjunker)  
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Final result: 7 21
This poll has been closed.
rfc/json_encode_indentation.txt · Last modified: 2022/07/19 15:23 by cmb