Implicitly marking parameter $... as nullable is deprecated in PHP
8.4. The explicit nullable type must be used instead.
Bug: T376276
Change-Id: I40bb7a0a02aaa467cbf0ae182adf5601ccbcb58e
* Add PHP type hints where possible.
* Remove @var, @param and @return if redundant to type declaration
* Remove redundant type conversions which are now enforced by type
hints.
* Enforce that decodeBoolean returns only a bool.
Change-Id: I8da84ed4dc778dd9d84f8d9eec0a399f5ed26405
