PHP Quick Scripting Reference

CHAPTER 18

Type Hinting

PHP relies on the proper documentation of functions for developers to know what arguments a function can take. To simplify this PHP 5 introduced type hinting, which allows a function to specify the type of arguments it accepts. Allowed types include classes, interfaces and the pseudo types array and callable.

Name	Description
class name	Argument must be an object of this class or a child.
interface name	Argument must be an object implementing this interface.
array	Argument must be an array.
callable	Argument must be callable as a function.

A type hint is set by prefixing the parameter with ...