pocketmine\level\Level::setBlockTempData PHP Method

    public function setBlockTempData(Vector3 $pos, $data = null)
    {
        if ($data == null and isset($this->blockTempData[self::blockHash($pos->x, $pos->y, $pos->z)])) {
            unset($this->blockTempData[self::blockHash($pos->x, $pos->y, $pos->z)]);
        } else {
            $this->blockTempData[self::blockHash($pos->x, $pos->y, $pos->z)] = $data;
        }
    }