Where is my mistake ?

This is the Problem:

[14:16:43] [Server thread/CRITICAL]: ParseError: "syntax error, unexpected ' ' (T_STRING), expecting '{'" (EXCEPTION) in "plugins/teleporter/src/fixed/Main" at line 16

And this is my Code:

<?php

namespace Server;

use pocketmine\plugin\PluginBase;
use pocketmine\event\Listener;
use pocketmine\command\CommandSender;
use pocketmine\command\Command;
use pocketmine\Player;
use pocketmine\plugin\Plugin;
use jojoe77777\FormAPI\SimpleForm;

class Main extends Listener{

public function openHelpUI(){
$form = new SimpleForm(function(Player $player, int $data = null) {});
$form->addbutton("§3Citybuild");
}
}

public function onCommand(CommandSender $sender, string $commandLabel, array $args) {
switch ($args[0]) {
case "tpuicity":
$this->openHelpUI($sender, "Menu Opened");
}
}

 

Your bracket's didn't match up, here I fixed it:

PHP:

<?php

namespace Server;

use pocketmine\plugin\PluginBase;
use pocketmine\event\Listener;
use pocketmine\command\CommandSender;
use pocketmine\command\Command;
use pocketmine\Player;
use pocketmine\plugin\Plugin;
use jojoe77777\FormAPI\SimpleForm;

class Main extends Listener {
  public function openHelpUI(){
    $form = new SimpleForm(function(Player $player, int $data = null) {}); 
    $form->addbutton("§3Citybuild");
  }

  public function onCommand(CommandSender $sender, string $commandLabel, array $args) {
    switch ($args[0]) {
      case "tpuicity":
      $this->openHelpUI($sender, "Menu Opened");
    }
  }
}


Please indent your code in the future and use an IDE to prevent errors like that