Class

Hack supports passing references to classes for use in instatiation and static member access.

<<__ConsistentConstruct>>
class Employee {
  public static function getKind(): int { return 4; };
}

function f(class<Employee> $cls): void {
  $w = new $cls();  // create an object of $cls

  $i = $cls::getKind();
}

Function f can be called with a reference to the class Employee or any of its subclasses using ::class literals (SomeClassName::class).

class Intern extends Employee {
  // ...
}

function demo(): void {
  f(Employee::class);  // will call: new Employee();
  f(Intern::class);    // will call: new Intern();
  f(Vector::class);    // typechecker error!
}