How to add subcommand player name

how do i make it so that for example i do
/test (playername)
sends to player hi

 

Its Really Simple

simply do this

PHP:

//this code gets the player from the first argument
$player = $this->getServer()->getPlayer($args[0]);
            if ($player == null) {// this code  checks if the player exists or is online
                $sender->sendMessage("That Player Is Not Online");//if not online tell the player sending the command they arent online
                return true;
            }
$player->sendMessage("hi");//if the player is online, it will send them the message