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Date: Thu, 2 Mar 2023 12:00:05 +0000
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Subject: Re: [PHP-DEV] RFC Idea - json_validate() validate schema
From: rowan.collins@gmail.com (Rowan Tommins)

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On Wed, 1 Mar 2023 at 11:44, juan carlos morales <dev.juan.morales@gmail.com>
wrote:

> I am thinking about enhancing this function to also be able to
> validate against a JSON SCHEMA, giving us something like this:
>
> json_validate(string $json, int $depth = 512, int $flags = 0, string
> $json_schema = null): bool
>


Functionally, I think this is sounds great. My only concern is that JSON
Schema is a bit of a moving target. Unlike XSD, which has only ever had two
revisions, 10 years apart (1.0 from 2001, and 1.1 from 2012), JSON Schema
is in active development, with "Draft-07", "2019-09", and "2020-12" all
seeing deployment as stable releases, and work in progress on a new
version: https://github.com/json-schema-org/json-schema-spec/milestone/7

That raises two questions:

* Which existing version(s) of the specification will be implemented? For
instance, if I have a schema written for 2019-09 rather than 2020-12, will
I be able to use this validator?
* How will new versions of the specification be added to the parser? If PHP
8.4 is release in November 2024, and JSON Schema 2025-01 is published two
months later, will I need to wait for PHP 8.5 to use the new specification?

I guess the combination of those leads to a third question: will support
for some versions be *removed* in later PHP versions, so that each PHP
version will have a minimum and maximum schema version it supports?

That's the big disadvantage of anything shipped in core, rather than in an
extension or library - there is no way to make even minor changes outside
of PHP's release cycle.

I wonder if there's some way this can be made pluggable - ship the core
mechanisms needed by the validator in core, but make them accessible to
libraries to implement specific specifications in an efficient way. This is
the approach taken by the MongoDB PHP driver - there's a stable extension
providing efficient low-level routines, then a decoupled PHP library which
can be installed at the project level, and follow a much more agile release
process. I'm not sure what it would look like in this case, but may be
worth considering.

Regards,
-- 
Rowan Tommins
[IMSoP]

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