pocketmine\event\entity\EntityDamageEvent::getDamage PHP Method

    public function getDamage($type = self::MODIFIER_BASE)
    {
        if (isset($this->modifiers[$type])) {
            return $this->modifiers[$type];
        }
        return 0;
    }

 public function onDeath(EntityDamageEvent $event)
 {
     $damage = $event->getDamage();
     $health = $event->getDamager()->getHealth();
     if ($health <= $damage) {
         $player = $event->getDamager();
         $money = $this->getConfig()->get("money");
         $player->sendMessage("You've Earned 8 Coins");
         $this->addMoney($player->getName(), $money);
     }
 }