pocketmine\command\CommandSender::sendMessage PHP Method

    public function sendMessage($message);

 public function onCommand(CommandSender $sender, Command $command, $label, array $args)
 {
     if ($sender instanceof Player) {
         if (count($args) == 0) {
             $sender->sendMessage(TextFormat::RED . "Not enough arguments.");
             return;
         }
         if (count($args) == 1) {
             if ($this->getServer()->getPlayer($args[0])) {
                 $location = $this->getServer()->getPlayer($args[0])->getLocation();
                 $sender->teleport($location);
                 $sender->sendMessage(TextFormat::BLUE . "[Server] You have teleported to {$args['0']}");
                 return;
             } else {
                 $sender->sendMessage(TextFormat::RED . "[Server] That player isn't online!");
                 return;
             }
         }
         if (count($args) == 2) {
             if ($this->getServer()->getPlayer($args[0]) & getLocation() && $this->getServer()->getPlayer($args[1])) {
                 $location2 = $this->getServer()->getPlayer($args[1])->getLocation();
                 $player1 = $this->getServer()->getPlayer($args[0]);
                 $player2 = $this->getServer()->getPlayer($args[1]);
                 $player1->teleport($location2);
                 $player1->sendMessage(TextFormat::BLUE . "[Server] You have teleported to {$args['1']}");
                 return;
             }
         }
     }
 }