PHP 8.4 Fix implicitly nullable parameter declarations deprecations

[Art4]

This PR fixes the PHP 8.4 deprecation warnings for implicitly nullable parameter declarations, see https://php.watch/versions/8.4/implicitly-marking-parameter-type-nullable-deprecated

PHP 8.4 deprecates implicitly nullable types. PHP applications are recommended to explicitly declare the type as nullable. All type declarations that have a default value of null, but without declaring null in the type declaration emit a deprecation notice

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.47%. Comparing base (31768d5) to head (cc14f15).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## v2.x #407 +/- ## ========================================= Coverage 98.47% 98.47% Complexity 609 609 ========================================= Files 29 29 Lines 1841 1841 ========================================= Hits 1813 1813 Misses 28 28 ```

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