[PHP] Fix deprecations in PHP 8.1

Created by: satackey

Fixed the following deprecations in PHP 8.1. This pull request resolves #11742 (closed).

Deprecated: Return type of XXXX::offsetExists($offset) should either be compatible with ArrayAccess::offsetExists(mixed $offset): bool, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in ...

Added the #[\ReturnTypeWillChange] attribute or the same type hint as the internal interface to the return value of methods that implement PHP's internal interface ArrayAccess.

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