php正则判断是否为合法身份证号的方法

/**
 * 判断是否为合法的身份证号码
 * @param $mobile
 * @return int
 */
function isCreditNo($vStr){
 $vCity = array(
  '11','12','13','14','15','21','22',
  '23','31','32','33','34','35','36',
  '37','41','42','43','44','45','46',
  '50','51','52','53','54','61','62',
  '63','64','65','71','81','82','91'
 );
 if (!preg_match('/^([\d]{17}[xX\d]|[\d]{15})$/', $vStr)) return false;
 if (!in_array(substr($vStr, 0, 2), $vCity)) return false;
 $vStr = preg_replace('/[xX]$/i', 'a', $vStr);
 $vLength = strlen($vStr);
 if ($vLength == 18) {
  $vBirthday = substr($vStr, 6, 4) . '-' . substr($vStr, 10, 2) . '-' . substr($vStr, 12, 2);
 } else {
  $vBirthday = '19' . substr($vStr, 6, 2) . '-' . substr($vStr, 8, 2) . '-' . substr($vStr, 10, 2);
 }
 if (date('Y-m-d', strtotime($vBirthday)) != $vBirthday) return false;
 if ($vLength == 18) {
  $vSum = 0;
  for ($i = 17 ; $i >= 0 ; $i--) {
   $vSubStr = substr($vStr, 17 - $i, 1);
   $vSum += (pow(2, $i) % 11) * (($vSubStr == 'a') ? 10 : intval($vSubStr , 11));
  }
  if($vSum % 11 != 1) return false;
 }
 return true;
}