[PHP-DEV] [Pre-RFC] Opt-in JSON comments and trailing commas

Mailing Lists php.internals
1

Hello!

I would like to discuss a draft RFC that adds two independent and opt-in flags to ext/json for PHP 8.7:

  • JSON_ALLOW_COMMENTS
  • JSON_ALLOW_TRAILING_COMMAS

Both flags would be accepted by json_decode() and json_validate(). Strict JSON would remain the default. Comments are limited to // and non-nesting /* … */ at JSON whitespace boundaries. Trailing commas permit one comma after the last element or member of a nonempty array or object.

The implementation processes comments in the existing re2c scanner. It handles trailing commas in the existing Bison grammar. It does not preprocess or copy the input, so it preserves strings and original source locations. The RFC uses two primary votes so that either extension can be accepted independently.

Draft implementation is located here: https://github.com/php/php-src/pull/23336

Recently I also published a similar PHP library: https://github.com/otar/jsonc

I would particularly appreciate feedback on the API names and the inclusion of json_validate(). Feedback on the specified UTF-8, control-character, and error-location behavior would also be useful.

Otar

2

On Mon, Aug 17, 2026, at 1:18 PM, Otar Chekurishvili wrote:

Hello!

I would like to discuss a draft RFC that adds two independent and
opt-in flags to ext/json for PHP 8.7:

- JSON_ALLOW_COMMENTS
- JSON_ALLOW_TRAILING_COMMAS

Both flags would be accepted by json_decode() and json_validate().
Strict JSON would remain the default. Comments are limited to // and
non-nesting /* ... */ at JSON whitespace boundaries. Trailing commas
permit one comma after the last element or member of a nonempty array
or object.

The implementation processes comments in the existing re2c scanner. It
handles trailing commas in the existing Bison grammar. It does not
preprocess or copy the input, so it preserves strings and original
source locations. The RFC uses two primary votes so that either
extension can be accepted independently.

Draft implementation is located here: JSON: Add opt-in comments and trailing comma flags by otar · Pull Request #23336 · php/php-src · GitHub

Recently I also published a similar PHP library: GitHub - otar/jsonc: JSONC parser for PHP · GitHub

I would particularly appreciate feedback on the API names and the
inclusion of json_validate(). Feedback on the specified UTF-8,
control-character, and error-location behavior would also be useful.

Otar

Does this essentially mean JSON5 support? If so, just call it that. (I am undecided on the best way to support that.)

--Larry Garfield

3

On 17/08/2026 21:54, Larry Garfield wrote:

Does this essentially mean JSON5 support? If so, just call it that. (I am undecided on the best way to support that.)

--Larry Garfield

That is a language known as Microsoft's JSONC or Nigel Tao's JWCC (JSON with Comments and Commas) they are effectively equivalent. JSON5 would also require single quotes, unquoted keys, NAN and +/-INF values, multiline strings, and some other minor stuff I don't even remember

--
Anton