Worked on the JetBrains/phpstorm-stubs repository to address a regression affecting type hinting for the implode and join functions in PHP. Focused on restoring the nullable type hint for the second parameter, which had previously been removed, the developer used code reversion techniques to ensure that array parameters could once again be nullable as expected by PHP’s type system. This fix improved the stability and correctness of static analysis and code completion within the IDE. The work involved PHP development and careful validation to align with language standards, with changes documented and traceable through a single, auditable commit for maintainability.