pocketmine\inventory\EnchantInventory::onOpen PHP Метод

    public function onOpen(Player $who)
    {
        parent::onOpen($who);
        if ($this->levels == null) {
            $this->bookshelfAmount = $this->countBookshelf();
            if ($this->bookshelfAmount < 0) {
                $this->bookshelfAmount = 0;
            }
            if ($this->bookshelfAmount > 15) {
                $this->bookshelfAmount = 15;
            }
            $base = mt_rand(1, 8) + $this->bookshelfAmount / 2 + mt_rand(0, $this->bookshelfAmount);
            $this->levels = [0 => max($base / 3, 1), 1 => $base * 2 / 3 + 1, 2 => max($base, $this->bookshelfAmount * 2)];
        }
    }