Duplicate Type¶
Union types check for duplicate types, so array|array is not possible, nor if a class is aliased with a use expression: on the other hand, it is valid with a class alias, created with class_alias().
The last case is the union type that actually hides the type: here, iterable includes array, so PHP complains about a duplicate, which is not visible at first sight.
Note that intersectional types also check for duplicate types.
See Also¶
Duplicate types [Try me]