Custom Item Names

This is my current code:

PHP:

        public function playerItemHeld(PlayerItemHeldEvent $event){
        $item = $event->getItem();
        $player = $event->getPlayer();
        if ($item instanceof Item){
            switch ($item->getId()){
                case 378: ETC...

Do I add $item->setCustomName(NAME)? And would it look like this?

PHP:

        public function playerItemHeld(PlayerItemHeldEvent $event){
        $item = $event->getItem();
        $player = $event->getPlayer();
        if ($item instanceof Item){
                $item->setCustomName(TextFormat::GREEN . "NAME");
            switch ($item->getId()){
                case 378: ETC....

So I tried that and it's not changing the name. I could send a tip or a PopUp but there are still a few hundred milliseconds before that would happen and you would see the item's name.

https://forums.pocketmine.net/threads/custom-item-name.11815/

PHP:

$item = $event->getItem()->getId();



He is using the Item object here. Why should he getId()? Please don't post if you don't understand what you are talking about.