pocketmine\level\SimpleChunkManager::setBlockIdAt PHP Method

    public function setBlockIdAt(int $x, int $y, int $z, int $id)
    {
        if ($chunk = $this->getChunk($x >> 4, $z >> 4)) {
            $chunk->setBlockId($x & 0xf, $y & 0x7f, $z & 0xf, $id);
        }
    }