Iterable is a pseudo-type introduced in PHP 7.1. It accepts any &array; or object implementing the Traversable interface. Both of these types are iterable using &foreach; and can be used with yield from within a generator. Iterable can be used as a parameter type to indicate that a function requires a set of values, but does not care about the form of the value set since it will be used with &foreach;. If a value is not an array or instance of Traversable, a TypeError will be thrown. ]]> Parameters declared as iterable may use &null; or an array as a default value. ]]> Iterable can also be used as a return type to indicate a function will return an iterable value. If the returned value is not an array or instance of Traversable, a TypeError will be thrown. ]]> Functions declaring iterable as a return type may also be generators. ]]>