I want to ban specific command

I want to ban "/me" command

public function onPlayerCommandProcessEvent (PlayerCommandPreprocessEvent $ev) {

$player = $ev->getPlayer();
$message = $ev->getMessage();
$words = explode(" ", $message);
$cmd = strtolower(substr(array_shift($words), 1));

if ($cmd === "me") {
$player->sendMessage("§b§o[ Notice ] §7You can't use this command");
}

}

This source doesn't work. What is wrong?

 

I solved already this problem. Thank you to answer