pocketmine\utils\Binary::readLDouble PHP Method

    public static function readLDouble($str)
    {
        return ENDIANNESS === self::BIG_ENDIAN ? unpack("d", strrev($str))[1] : unpack("d", $str)[1];
    }

 public function getDouble()
 {
     return $this->endianness === self::BIG_ENDIAN ? Binary::readDouble($this->get(8)) : Binary::readLDouble($this->get(8));
 }