PHP 8.4 support (Implicitly marking parameter $request as nullable is deprecated, the explicit nullable type must be used instead)

[puzzledmonkey]

This PR adds support for PHP8.4, which has changed how we need to define nullable function parameters - they must be marked explicitly now (i.e. Service|null $service = null instead of just Service $service = null)

I've tried to minimise the code changes and stick with the code style (i.e. Service|null instead of ?Service) of the original files but please let me know if there is anything you would like to to fix/revisit/explain more.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[Jubeki]

@puzzledmonkey Support for Union Types was only added in PHP 8.0:
See https://www.php.net/manual/en/language.types.declarations.php

This library supports PHP >= 7.2.5.

To support PHP 8.4 and keep backwards compatibility you would need the ?, which was added in PHP 7.1. I also attempted a PR #2995 with that in mind, so maybe that PR can be reviewed, or a new one be attempted.

For the maintainers:
The explicit nullable type (?) is fully backwards compatible and contain no breaking changes.
See the following article: https://php.watch/versions/8.4/implicitly-marking-parameter-type-nullable-deprecated#change

The explicit declaration is compatible with PHP 7.1 and later, even if you extend the class.

You can also take a look at the following snippet at PHP Playground at php-play.dev

<?php

class ParentClass {
   public function tester(?string $value = null) {}
}

// This class is compatible after PHP 7.1, because it keeps the null type implicitly.
class SubClass extends ParentClass {
     public function tester(string $value = null) {}
}

// This class is compatible after PHP 7.1, because it keeps the null type explicitly.
class SubClass2 {
   public function tester(?string $value) {}
}

// Fatal Error: This class is not compatible with the parent class even before PHP 8.4,
// because the implicit null type is removed from the declaration.
class SubClass3 extends ParentClass {
     public function tester(string $value) {}
}

// Fatal Error: This class is not compatible with the parent class even before PHP 8.4,
// because the implicit null type is removed from the declaration.
class SubClass4 extends ParentClass {
     public function tester(string $value = 'x') {}
}

[puzzledmonkey]

Sorry @Jubeki I didn't spot your PR for some reason (I did search!) so I'll close this one now.

[Jubeki]

@puzzledmonkey you can keep your PR open. My PR was closed, so it would be great if another PR is considered.

[puzzledmonkey]

This PR also now uses the backwards-compatible ? syntax rather than |null, and this should therefore mean this PR has no breaking changes at all, and just adds forwards-compatibility for PHP 8.4

[yenfryherrerafeliz]

Hi @puzzledmonkey, thanks for your contribution. I will be closing this PR in favor of this one which was opened a bit earlier for addressing this. Please track any further updates there.

Thanks!