pocketmine\network\protocol\ContainerSetContentPacket::encode PHP Method

    public function encode()
    {
        $this->reset();
        $this->putByte($this->windowid);
        $this->putShort(count($this->slots));
        foreach ($this->slots as $slot) {
            $this->putSlot($slot);
        }
        if ($this->windowid === self::SPECIAL_INVENTORY and count($this->hotbar) > 0) {
            $this->putShort(count($this->hotbar));
            foreach ($this->hotbar as $slot) {
                $this->putInt($slot);
            }
        } else {
            $this->putShort(0);
        }
    }