pocketmine\Server::getGamemodeString PHP Method

    public static function getGamemodeString($mode)
    {
        switch ((int) $mode) {
            case Player::SURVIVAL:
                return "%gameMode.survival";
            case Player::CREATIVE:
                return "%gameMode.creative";
            case Player::ADVENTURE:
                return "%gameMode.adventure";
            case Player::SPECTATOR:
                return "%gameMode.spectator";
        }
        return "UNKNOWN";
    }

 public function execute(CommandSender $sender, $currentAlias, array $args)
 {
     if (!$this->testPermission($sender)) {
         return true;
     }
     if (count($args) === 0) {
         $sender->sendMessage(new TranslationContainer("commands.generic.usage", [$this->usageMessage]));
         return false;
     }
     $gameMode = Server::getGamemodeFromString($args[0]);
     if ($gameMode !== -1) {
         $sender->getServer()->setConfigInt("gamemode", $gameMode);
         $sender->sendMessage(new TranslationContainer("commands.defaultgamemode.success", [Server::getGamemodeString($gameMode)]));
     } else {
         $sender->sendMessage("Unknown game mode");
     }
     return true;
 }