EU VAT Number validation

vatvalidation.php

<?php

$pattern = "/^(AT|B[GE]|C[YZ]|D[EK]|E[ELS]|F[IR]|GB|H[RU]|I[ET]|L[TUV]|MT|NL|P[LT]|RO|S[EIK])([A-Z]|[0-9])+$/";
$vatnumber = strtoupper($_REQUEST['q']);
$value = $vatnumber;
if (preg_match($pattern, $vatnumber)){
  // Create validation request to VIES service
  $country_code = substr($vatnumber, 0, 2);
  $vatnum = substr($vatnumber, 2, strlen($vatnumber)-2);
  $client = new SoapClient("http://ec.europa.eu/taxation_customs/vies/checkVatService.wsdl");
  $response = (array)$client->checkVat(array('countryCode' => $country_code,'vatNumber' => $vatnum));
  if ($response['valid']) {
    // VAT number is valid
    // $response holds extra information about the company
  } else {
    // VAT number is invalid
  }
} else {
  // Invalid VAT number format
}