public function toBytes()
{
if (gmp_cmp($this->value, gmp_init(0)) === 0) {
return '';
}
$temp = gmp_strval(gmp_abs($this->value), 16);
$temp = mb_strlen($temp, '8bit') & 1 ? '0' . $temp : $temp;
$temp = hex2bin($temp);
return ltrim($temp, chr(0));
}