Interfaces and Access Levels

I would like bar::do_something_internal() to have an access level of *private* But this would fail, as the interface can only have *public* methods. Is there a way to get bar::do_something_internal() to be private? Or am I SOL, and it has be public? Thanks interface foo {

    function do_something_internal();

} class bar implements foo { private function do_something_internal() {

       // I would like this to be private

} }