mixed Type

Just like iterable is a shorthand for the union type array|Traversable, the new mixed type is a shorthand for all types except for classes and interfaces as well as void:


The mixed type was introduced to enable developers to indicate in code that the type of a parameter, return value, property, etc. cannot be specified more precisely. Without such an indication, the absence of type information could be interpreted as “the developers do not care about type safety”.