银行卡luhn算法失效

$number = '6214832018989180';
$parity = strlen($number) % 2;
$total = 0;
// Split each digit into an array
$digits = str_split($number);
foreach ($digits as $key => $digit) { // Foreach digit
    // for every second digit from the right most, we must multiply * 2
    if (($key % 2) == $parity)
        $digit = ($digit * 2);
    // each digit place is it's own number (11 is really 1 + 1)
    if ($digit >= 10) {
        // split the digits
        $digit_parts = str_split($digit);
        // add them together
        $digit = $digit_parts[0] + $digit_parts[1];
    }
    // add them to the total
    $total += $digit;
}
$r = ($total % (false ? 5 : 10) == 0 ? true : false);


//解决方法使用支付宝接口：可查询银行卡相关信息，从而验证银行卡有效

//https://ccdcapi.alipay.com/validateAndCacheCardInfo.json?_input_charset=utf-8&cardNo=6214832018989180&cardBinCheck=true