pocketmine\level\GameRules::hasRule PHP Method

    public function hasRule($name)
    {
        return array_key_exists($name, $this->getRulesArray());
    }

 public function setGameRule($name, $value)
 {
     $this->gamerules->setOrCreateGameRule($name, $value);
     return $this->gamerules->hasRule($name);
 }