This isn't a matter of syntax, it's a matter of semantics. The syntax isn't in question, the semantics of forcing the user to pass an empty value to get to the next useful parameter is the issue. "we can already pass $null there" is easy for someone who knows the API to say. Please tell me how you would explain this to someone who has never used $tip before, and potentially doesn't know what $null is. I can't think of any way this can be documented without seeming insanely confusing to a user who doesn't know the language extremely well.