isInternal()) { echo "Internal Function\n"; } else { echo "User-defined Function\n"; } ?>In the code example, the ReflectionFunction class is used to inspect the "myFunction" function. If the function is a built-in PHP function, the code will output "Internal Function". Otherwise, it will output "User-defined Function". The ReflectionFunction class is part of PHP's reflection API, which is included in the "Reflection" package in PHP.