This is in the docs http://www.php.net/manual/en/class.reflectionparameter.php and is used by Symfony
ReflectoinParamenter was fetching both type and type hint from the same field. That created an incompatible change with existing code and broke the mocking framework. Separated the type and type hint field to contain the possible different values.
These names don't make sense now that we run both suites the same way.