These types declarations can only be used within classes.
The value must be an instanceof
the same class as the one
in which the type declaration is used.
The value must be an instanceof
a parent of the class
in which the type declaration is used.
static is a return-only type which requires that the
value returned must be an instanceof
the same class as the one
the method is called in.
Available as of PHP 8.0.0.