Silence PHP 8.4 deprecations regarding implicitly nullable parameters

[mbabker]

This PR updates the library to silence deprecation notices on PHP 8.4 with implicitly nullable parameters. To try and keep the code diff as small as possible, here's what I did:

• Bumped PHPUnit dev dependency to latest 9.6 release to ensure all dev dependencies will install with PHP 8.4 (it was previously locked to a transient set of dependencies that couldn't install on PHP 8.2 or later)
• Bumped PHP-CS-Fixer to latest minor version (as this is a CS tool it doesn't really need to have a wide version range)
• Ran composer update with the PHP platform config set to 8.1.33 to keep the lockfile compatible with PHP 8.1
• Ran PHP-CS-Fixer with the config below
  • Note all the random whitespace additions/removals are from the fixer as well)
• Ran PHPUnit to ensure there weren't any deprecations printed out (and fixed the one dynamic property deprecation that was shown)
• Committed

<?php declare(strict_types=1);

return (new PhpCsFixer\Config())
    ->setParallelConfig(PhpCsFixer\Runner\Parallel\ParallelConfigFactory::detect())
    ->setRules([
        '@PSR12' => true,
        'nullable_type_declaration_for_default_null_value' => [
            'use_nullable_type_declaration' => true,
        ],
    ])
    ->setFinder(
        (new PhpCsFixer\Finder())
            ->in(__DIR__)
            ->ignoreDotFiles(true)
            ->ignoreVCS(true)
    );

[boelew]

Thanks for this work! I was having the same issues since I upgraded my system to php8.4 and was trying to solve them myself. Quickly found that you did the work already.

I had a look at your changes and it would have my approval.

[stevleibelt]

@alexdebril please merge this and create a release.

[thedotedge]

Any chance to merge this and cut a new version?