/**
* prüft die Umsatzsteueridentnummer aufgrund von Strukturmerkmalen
* der einzelnen Länder
*
* @param string $ustid
* @return bool valid or not
*/
function checkUstId($ustid)
{
  $u = strtoupper(preg_replace('~\W~', '', $ustid));
  $country = substr($u, 0, 2);
  switch ($country)
  {
    case 'AT':
      return (preg_match('~^ATU[A-Z0-9]{8,8}$~', $u) !== 0);
    break;
    case 'BE':
    return (preg_match('~^BE0[0-9]{9,9}$~', $u) !== 0);
    break;
    case 'BG':
    return (preg_match('~^BG[0-9]{9,10}$~', $u) !== 0);
    break;
    case 'CY':
    return (preg_match('~^CY[A-Z0-9]{9,9}$~', $u) !== 0);
    break;
    case 'CZ':
    return (preg_match('~^CZ[0-9]{8,10}$~', $u) !== 0);
    break;
    case 'DE':
    return (preg_match('~^DE[0-9]{9,9}$~', $u) !== 0);
    break;
    case 'DK':
    return (preg_match('~^DK[0-9]{8,8}$~', $u) !== 0);
    break;
    case 'EE':
    return (preg_match('~^EE[0-9]{9,9}$~', $u) !== 0);
    break;
    case 'EL':
    return (preg_match('~^EL[0-9]{9,9}$~', $u) !== 0);
    break;
    case 'ES':
    return (preg_match('~^ES[A-Z0-9]{1,1}[0-9]{7,7}[A-Z0-9]{1,1}$~', $u) !== 0);
    break;
    case 'FI':
    return (preg_match('~^FI[0-9]{8,8}$~', $u) !== 0);
    break;
    case 'FR':
    return (preg_match('~^FR[A-Z0-9]{2,2}[0-9]{9,9}$~', $u) !== 0);
    break;
    case 'GB':
    $result = (preg_match('~^GB[0-9]{9,9}$~', $u) !== 0);
    if ($result)
    return true;
    $result = (preg_match('~^GB[0-9]{12,12}$~', $u) !== 0);
    if ($result)
    return true;
    $result = (preg_match('~^GBGD[0-9]{3,3}$~', $u) !== 0);
    if ($result)
    return true;
    return (preg_match('~^GBHA[0-9]{3,3}$~', $u) !== 0);
    break;
    case 'HU':
    return (preg_match('~^HU[0-9]{8,8}$~', $u) !== 0);
    break;
    case 'IE':
    return (preg_match('~^IE[A-Z0-9]{8,8}$~', $u) !== 0);
    break;
    case 'IT':
    return (preg_match('~^IT[0-9]{11,11}$~', $u) !== 0);
    break;
    case 'LT':
    $result = (preg_match('~^LT[0-9]{9,9}$~', $u) !== 0);
    if ($result)
    return true;
    return (preg_match('~^LT[0-9]{12,12}$~', $u) !== 0);
    break;
    case 'LU':
    return (preg_match('~^LU[0-9]{8,8}$~', $u) !== 0);
    break;
    case 'LV':
    return (preg_match('~^LV[0-9]{11,11}$~', $u) !== 0);
    break;
    case 'MT':
    return (preg_match('~^MT[0-9]{8,8}$~', $u) !== 0);
    break;
    case 'NL':
    return (preg_match('~^NL[A-Z0-9]{9,9}B[A-Z0-9]{2,2}$~', $u) !== 0);
    break;
    case 'PL':
    return (preg_match('~^PL[0-9]{10,10}$~', $u) !== 0);
    break;
    case 'PT':
    return (preg_match('~^MT[0-9]{9,9}$~', $u) !== 0);
    break;
    case 'RO':
    return (preg_match('~^RO[0-9]{2,10}$~', $u) !== 0);
    break;
    case 'SE':
    return (preg_match('~^SE[0-9]{12,12}$~', $u) !== 0);
    break;
    case 'SI':
    return (preg_match('~^SI[0-9]{8,8}$~', $u) !== 0);
    break;
    case 'SK':
    return (preg_match('~^SK[0-9]{10,10}$~', $u) !== 0);
    break;
  }
  return false;
}