PHP 檢查信用卡號碼

以前寫過身份證字號的驗證程式...
自從有信用卡後...就常在想怎麼驗證信用卡號..
今天總算看到了...特別摘錄一下
參考資料來源：PHP 檢查信用卡號碼



PHP:
/* luhn_checker(): This is a small PHP function for checking valid *
* credit card with LUHN algorithm *
* *
* Last updated: 26 August 2007 *
* This is a free PHP script under GNU GPL version 2.0 or above *
* Copyright (C) 2007 Sam Tang *
* Feedback/comment/suggestions : http://www.real-blog.com/ */

function luhn_checker($card_num){
// 將非數字的字串移除
$card_num = preg_replace("/\D|\s/", "", $card_num);

$sum = 0;
for($i=0; $i $digit = substr($card_num, $i, 1);
if(($i % 2) == 0){
// 在單數位置的數值乘 2
$digit = $digit * 2;
}

if ($digit> 9) $digit = $digit - 9;
$sum += $digit;
}

if(($sum % 10) == 0 && strlen($card_num) == 16){
return TRUE;
}else{
return FALSE;
}
}

/* Example
if(luhn_checker("1234567812345678")){
echo "Correct!";
}else{
echo "Wrong card number!";
}
*/
?>