pocketmine\block\Fallable::onUpdate PHP Method

    public function onUpdate($type)
    {
        if ($type === Level::BLOCK_UPDATE_NORMAL) {
            $down = $this->getSide(Vector3::SIDE_DOWN);
            if ($down->getId() === self::AIR or $down instanceof Liquid) {
                $fall = Entity::createEntity("FallingSand", $this->getLevel()->getChunk($this->x >> 4, $this->z >> 4), new CompoundTag("", ["Pos" => new ListTag("Pos", [new DoubleTag("", $this->x + 0.5), new DoubleTag("", $this->y), new DoubleTag("", $this->z + 0.5)]), "Motion" => new ListTag("Motion", [new DoubleTag("", 0), new DoubleTag("", 0), new DoubleTag("", 0)]), "Rotation" => new ListTag("Rotation", [new FloatTag("", 0), new FloatTag("", 0)]), "TileID" => new IntTag("TileID", $this->getId()), "Data" => new ByteTag("Data", $this->getDamage())]));
                $fall->spawnToAll();
            }
        }
    }