Yes. We want to spend as little time as possible on code so we can quickly find the data structure that best solves the problem we have yet to understand. //

Yes. We want to spend as little time as possible on code so we can quickly find the data structure that best solves the problem we have yet to understand. // I know nothing. Not sure what types would work best... public function method($data) // I know more public function method($data array) // More public function method($data array|false) // Even more public function method($data array|false) : int // Ah. Okay. I understand the problem domain and have proper data structures to solve it public function method($data array|false) : int|float Notice the type system never got in our way. We organically grew into the type system as our understanding of the data evolved.