Pseudo-type¶

A pseudo-type is a keyword and a type that describes an input or output, but is not an actual type.

For example, iterable represents both array and Traversable objects, yet a variable cannot be both, not be instantiated as such.

Union type, DNF or intersectional types are not pseudo-types, as they are made of multiple keywords.

There are several pseudo-type: mixed, callable, object, iterable.

<?php

function foo(iterable $a) { }

foo([]); // OK
foo(new ArrayIterator([1])); // OK
foo(1); // KO

?>