pocketmine\level\format\mcregion\Chunk::getBlockSkyLight PHP Method

    public function getBlockSkyLight($x, $y, $z)
    {
        $sl = ord($this->skyLight[$x << 10 | $z << 6 | $y >> 1]);
        if (($y & 1) === 0) {
            return $sl & 0xf;
        } else {
            return $sl >> 4;
        }
    }