pocketmine\item\Item::setCustomName PHP Method

    public function setCustomName(string $name)
    {
        if ($name === "") {
            $this->clearCustomName();
        }
        if (!($hadCompoundTag = $this->hasCompoundTag())) {
            $tag = new CompoundTag("", []);
        } else {
            $tag = $this->getNamedTag();
        }
        if (isset($tag->display) and $tag->display instanceof CompoundTag) {
            $tag->display->Name = new StringTag("Name", $name);
        } else {
            $tag->display = new CompoundTag("display", ["Name" => new StringTag("Name", $name)]);
        }
        if (!$hadCompoundTag) {
            $this->setCompoundTag($tag);
        }
        return $this;
    }

 public function setRPGItem(Item $item, $name, $desc, $class)
 {
     $classData = self::$ITEM_CLASS[$class];
     $item->setCustomName($classData["COLOR"] . ToAruPG::getTranslation($classData["TID"]) . $name);
     $item->getNamedTag()->desc = new String("desc", $desc);
     return $item;
 }