pocketmine\event\inventory\FurnaceBurnEvent::getFuel PHP Method

    public function getFuel()
    {
        return $this->fuel;
    }

 public function onFurnaceBurn(FurnaceBurnEvent $event)
 {
     $fuelSkill = SkillManager::getSkillByItem($event->getFuel());
     if (count($fuelSkill) > 0) {
         $event->setCancelled();
     }
 }