PaymentSlip::unsignPaymentId

static function unsignPaymentId(string $hash): ?int
{
	try
	{
		$unsignedValue = (new Signer())->unsign($hash, self::SALT);
	}
	catch (BadSignatureException $e)
	{
		return null;
	}

	if ((string)((int)$unsignedValue) !== $unsignedValue)
	{
		return null;
	}

	return (int)$unsignedValue;
}