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;

}