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;
}