Some basic uses of PHP 7

Predefine value type of method or function: (Scalar Type Hints) [crayon-5ab620d60a92e168687142/] Note: need to add declare(strict_types = 1) very  top to generate Fatal error: Uncaught TypeError: Argument 1 passed to double() must be of the type integer, string given. Predefine function or method  return value by adding ":  type" beside function name  . [crayon-5ab620d60a93a723718458/] Note: need [...]