Was ist das Meaninig von Hohlraumfunktionen in PHP

PHP
//in php the function must not return any things and
//just must do somethings in function
//so we declare function is this way :)
class A{
  public function __construct () {}
  
  public function test () :void {
  	$this->name = "mohamad";
	}
  
}
Mohamad