pocketmine\entity\Zombie::attack PHP Method

    public function attack($damage, EntityDamageEvent $source)
    {
        parent::attack($damage, $source);
        if ($source instanceof EntityDamageByEntityEvent) {
            $e = $source->getDamager();
            $deltaX = $this->x - $e->x;
            $deltaZ = $this->z - $e->z;
            $this->knockBack($e, $damage, $deltaX / 100, $deltaZ / 100, $source->getKnockBack());
        }
    }