This doesn't require any external package libraries, just the PHP interpreter itself. As for determining package libraries, this would depend on the specific application being developed. Some common PHP libraries that are frequently used include: - Composer (dependency manager) - Laravel (web application framework) - PHPUnit (unit testing framework) - Twig (template engine) To determine package libraries for a specific application, the developer would need to decide what functionality they need and research available packages that provide that functionality.