Introducing schema component

[chr-hertel]

Moving over php-mcp/schema which is based on 2025-03-26/schema.ts

Would still apply changes:

• using library specific exception classes instead of native base classes
• switching to readonly classes
• adding phpstan types for array structures
• [still questionable] - do we need always need all five? construct, make, toArray, fromArray and jsonSerialize
  my2cents: the array structure is needed for json_encode and therefore the jsonSerialize that's the main use case for converting into array - and we have three different ways of constructing those value objects, why?
  my proposal would be to reduce the amount of methods per class to three:
  • __construct(...) for developers to instantiate
  • make(array $data): static for creation from array data
  • jsonSerialize(): array (this would reduce the need to array_map/toArray calls on subobjects since jsonSerialize works recursively)

WDYT @CodeWithKyrian - am I missing something?

Still WIP

[CodeWithKyrian]

Yep, I agree with this direction. toArray is mostly just serving jsonSerialize so no point keeping both.

On make(array $data), I’d lean toward sticking with fromArray() as the static factory for array data. make() works better as a convenient constructor alias for devs who prefer Response::make(...) over new Response(...). Of course, with PHP 8.4 now supporting new Response()->method() without the extra parentheses, that pattern is slowly becoming less necessary.

I’m fine with keeping make() if we see it as syntactic sugar, but I’m happy to drop it too if we want to slim things down.

[chr-hertel]

When thinking about updates over time, I feel keeping in sync __construct and make is a bit annoying - also because we're only downstream to that official schema here.

If you give me a 👍 I would update the PR like this:

• Lib specific exceptions
• Drop toArray in favor of jsonSerialize
• No changes to fromArray
• Drop make in favor of slimming down
• Add PHPStan array shapes

[chr-hertel]

we have this twice still, and also the method string is handled in multiple places, but that's to sort with #3

[chr-hertel]

Got merged into main with 6025f89