php验证身份证号码正确性

/**
 * 验证身份证号
 * @param $vStr
 * @return bool
 */
function isCreditNo($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;
}
//该片段来自于http://outofmemory.cn