PHP RFC: json_encode indentation

• Version: 1.0
• Date: 2021-06-03
• Author: Timon de Groot, tdegroot96@gmail.com
• Implementation: https://github.com/php/php-src/pull/7093
• Status: Draft

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 string|int and its default value is 4.

When a string is passed, that character sequence will be used for indentation, where it normally would be ' ' (4 spaces). Users passing a string must be aware that usage of invalid JSON characters in the indentation value will natually cause invalid formatted JSON data.

When an int is passed, 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;
echo json_encode(['unicode' => "supported"], JSON_PRETTY_PRINT, 512, '🚀🚀') . PHP_EOL;
echo json_encode(['tabs' => "better"], JSON_PRETTY_PRINT, 512, "\t") . PHP_EOL;
 
?>

{
    "behavior": "default"
}
{
  "key": 4,
  "other_key": [
    2
  ]
}
{
🚀🚀"unicode": "supported"
}
{
	"tabs": "better"
}

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

• next PHP 8.x

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.

Tests are written with the RFC