Making explosive snowballs.

I tried the ProjectileHitEvent, the ProjectileHitBlockEvent and the ProjectileHitEntityEvent and the EntityDespawnEvent. None of them worked. How to make exploasive snowballs?

 

PHP:

public function onProjectileHitBlock(ProjectileHitBlockEvent $event){
  if($event->getEntity() instanceof Snowball){
    $x = $event->getEntity()->getX();
    $y = $event->getEntity()->getY();
    $z = $event->getEntity()->getZ();

    $explosion = new Explosion(new Position($x, $y, $z, $event->getEntity()->getLevel()), 4);
    $explosion->explodeB();
  }
}