What is the best way to validate a credit card in PHP?
https://stackoverflow.com/questions/174730
-
05-07-2019 - |
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Given a credit card number and no additional information, what is the best way in PHP to determine whether or not it is a valid number?
Right now I need something that will work with American Express, Discover, MasterCard, and Visa, but it might be helpful if it will also work with other types.
Solution
There are three parts to the validation of the card number:
- PATTERN - does it match an issuers pattern (e.g. VISA/Mastercard/etc.)
- CHECKSUM - does it actually check-sum (e.g. not just 13 random numbers after "34" to make it an AMEX card number)
- REALLY EXISTS - does it actually have an associated account (you are unlikely to get this without a merchant account)
Pattern
- MASTERCARD Prefix=51-55, Length=16 (Mod10 checksummed)
- VISA Prefix=4, Length=13 or 16 (Mod10)
- AMEX Prefix=34 or 37, Length=15 (Mod10)
- Diners Club/Carte Prefix=300-305, 36 or 38, Length=14 (Mod10)
- Discover Prefix=6011,622126-622925,644-649,65, Length=16, (Mod10)
- etc. (detailed list of prefixes)
Checksum
Most cards use the Luhn algorithm for checksums:
Luhn Algorithm described on Wikipedia
There are links to many implementations on the Wikipedia link, including PHP:
<?
/* Luhn algorithm number checker - (c) 2005-2008 shaman - www.planzero.org *
* This code has been released into the public domain, however please *
* give credit to the original author where possible. */
function luhn_check($number) {
// Strip any non-digits (useful for credit card numbers with spaces and hyphens)
$number=preg_replace('/\D/', '', $number);
// Set the string length and parity
$number_length=strlen($number);
$parity=$number_length % 2;
// Loop through each digit and do the maths
$total=0;
for ($i=0; $i<$number_length; $i++) {
$digit=$number[$i];
// Multiply alternate digits by two
if ($i % 2 == $parity) {
$digit*=2;
// If the sum is two digits, add them together (in effect)
if ($digit > 9) {
$digit-=9;
}
}
// Total up the digits
$total+=$digit;
}
// If the total mod 10 equals 0, the number is valid
return ($total % 10 == 0) ? TRUE : FALSE;
}
?>
OTHER TIPS
From 10 regular expressions you can't live without in PHP:
function check_cc($cc, $extra_check = false){
$cards = array(
"visa" => "(4\d{12}(?:\d{3})?)",
"amex" => "(3[47]\d{13})",
"jcb" => "(35[2-8][89]\d\d\d{10})",
"maestro" => "((?:5020|5038|6304|6579|6761)\d{12}(?:\d\d)?)",
"solo" => "((?:6334|6767)\d{12}(?:\d\d)?\d?)",
"mastercard" => "(5[1-5]\d{14})",
"switch" => "(?:(?:(?:4903|4905|4911|4936|6333|6759)\d{12})|(?:(?:564182|633110)\d{10})(\d\d)?\d?)",
);
$names = array("Visa", "American Express", "JCB", "Maestro", "Solo", "Mastercard", "Switch");
$matches = array();
$pattern = "#^(?:".implode("|", $cards).")$#";
$result = preg_match($pattern, str_replace(" ", "", $cc), $matches);
if($extra_check && $result > 0){
$result = (validatecard($cc))?1:0;
}
return ($result>0)?$names[sizeof($matches)-2]:false;
}
Sample input:
$cards = array(
"4111 1111 1111 1111",
);
foreach($cards as $c){
$check = check_cc($c, true);
if($check!==false)
echo $c." - ".$check;
else
echo "$c - Not a match";
echo "<br/>";
}
This gives us
4111 1111 1111 1111 - Visa
It's probably better NOT to validate in code at your end. Send the card info right over to your payment gateway and then deal with their response. It helps them detect fraud if you don't do anything like Luhn checking first -- let them see the failed attempts.
PHP Code
function validateCC($cc_num, $type) {
if($type == "American") {
$denum = "American Express";
} elseif($type == "Dinners") {
$denum = "Diner's Club";
} elseif($type == "Discover") {
$denum = "Discover";
} elseif($type == "Master") {
$denum = "Master Card";
} elseif($type == "Visa") {
$denum = "Visa";
}
if($type == "American") {
$pattern = "/^([34|37]{2})([0-9]{13})$/";//American Express
if (preg_match($pattern,$cc_num)) {
$verified = true;
} else {
$verified = false;
}
} elseif($type == "Dinners") {
$pattern = "/^([30|36|38]{2})([0-9]{12})$/";//Diner's Club
if (preg_match($pattern,$cc_num)) {
$verified = true;
} else {
$verified = false;
}
} elseif($type == "Discover") {
$pattern = "/^([6011]{4})([0-9]{12})$/";//Discover Card
if (preg_match($pattern,$cc_num)) {
$verified = true;
} else {
$verified = false;
}
} elseif($type == "Master") {
$pattern = "/^([51|52|53|54|55]{2})([0-9]{14})$/";//Mastercard
if (preg_match($pattern,$cc_num)) {
$verified = true;
} else {
$verified = false;
}
} elseif($type == "Visa") {
$pattern = "/^([4]{1})([0-9]{12,15})$/";//Visa
if (preg_match($pattern,$cc_num)) {
$verified = true;
} else {
$verified = false;
}
}
if($verified == false) {
//Do something here in case the validation fails
echo "Credit card invalid. Please make sure that you entered a valid <em>" . $denum . "</em> credit card ";
} else { //if it will pass...do something
echo "Your <em>" . $denum . "</em> credit card is valid";
}
}
Usage
echo validateCC("1738292928284637", "Dinners");
More theoric information can be found here:
We can use the following to validate the credit card. It works perfectly for me.
protected function luhn($number)
{
// Force the value to be a string as this method uses string functions.
// Converting to an integer may pass PHP_INT_MAX and result in an error!
$number = (string)$number;
if (!ctype_digit($number)) {
// Luhn can only be used on numbers!
return FALSE;
}
// Check number length
$length = strlen($number);
// Checksum of the card number
$checksum = 0;
for ($i = $length - 1; $i >= 0; $i -= 2) {
// Add up every 2nd digit, starting from the right
$checksum += substr($number, $i, 1);
}
for ($i = $length - 2; $i >= 0; $i -= 2) {
// Add up every 2nd digit doubled, starting from the right
$double = substr($number, $i, 1) * 2;
// Subtract 9 from the double where value is greater than 10
$checksum += ($double >= 10) ? ($double - 9) : $double;
}
// If the checksum is a multiple of 10, the number is valid
return ($checksum % 10 === 0);
}
protected function ValidCreditcard($number)
{
$card_array = array(
'default' => array(
'length' => '13,14,15,16,17,18,19',
'prefix' => '',
'luhn' => TRUE,
),
'american express' => array(
'length' => '15',
'prefix' => '3[47]',
'luhn' => TRUE,
),
'diners club' => array(
'length' => '14,16',
'prefix' => '36|55|30[0-5]',
'luhn' => TRUE,
),
'discover' => array(
'length' => '16',
'prefix' => '6(?:5|011)',
'luhn' => TRUE,
),
'jcb' => array(
'length' => '15,16',
'prefix' => '3|1800|2131',
'luhn' => TRUE,
),
'maestro' => array(
'length' => '16,18',
'prefix' => '50(?:20|38)|6(?:304|759)',
'luhn' => TRUE,
),
'mastercard' => array(
'length' => '16',
'prefix' => '5[1-5]',
'luhn' => TRUE,
),
'visa' => array(
'length' => '13,16',
'prefix' => '4',
'luhn' => TRUE,
),
);
// Remove all non-digit characters from the number
if (($number = preg_replace('/\D+/', '', $number)) === '')
return FALSE;
// Use the default type
$type = 'default';
$cards = $card_array;
// Check card type
$type = strtolower($type);
if (!isset($cards[$type]))
return FALSE;
// Check card number length
$length = strlen($number);
// Validate the card length by the card type
if (!in_array($length, preg_split('/\D+/', $cards[$type]['length'])))
return FALSE;
// Check card number prefix
if (!preg_match('/^' . $cards[$type]['prefix'] . '/', $number))
return FALSE;
// No Luhn check required
if ($cards[$type]['luhn'] == FALSE)
return TRUE;
return $this->luhn($number);
}
The luhn algorithm is a checksum that can used to validate the format of a lot of credit card formats (and also Canadian social insurance numbers...)
The wikipedia article also links to many different implementations; here's a PHP one:
http://planzero.org/code/bits/viewcode.php?src=luhn_check.phps
There is a PEAR package which handles the validation of many financial numbers, also credit card validation: http://pear.php.net/package/Validate_Finance_CreditCard
By the way, here are some Test Credit Card Account Numbers by PayPal.
Just throwing in some further code snippets that others may find useful (not PHP code).
PYTHON (single line code; probably not that efficient)
To validate:
>>> not(sum(map(int, ''.join(str(n*(i%2+1)) for i, n in enumerate(map(int, reversed('1234567890123452'))))))%10)
True
>>> not(sum(map(int, ''.join(str(n*(i%2+1)) for i, n in enumerate(map(int, reversed('1234567890123451'))))))%10)
False
To return the required check digit:
>>> (10-sum(map(int, ''.join(str(n*(i%2+1)) for i, n in enumerate(map(int, reversed('123456789012345')), start=1)))))%10
2
>>> (10-sum(map(int, ''.join(str(n*(i%2+1)) for i, n in enumerate(map(int, reversed('234567890123451')), start=1)))))%10
1
MySQL Functions
Functions "ccc" and "ccd" (credit-card-check and credit-card-digit)
Note that the "ccc" function has an additional check where if the calculated sum is 0, the returned result will always be FALSE, so an all zero CC number will never validate as being correct (under normal behaviour, it would validate correctly). This feature can be added/removed as required; maybe useful, depending on specific requirements.
DROP FUNCTION IF EXISTS ccc;
DROP FUNCTION IF EXISTS ccd;
DELIMITER //
CREATE FUNCTION ccc (n TINYTEXT) RETURNS BOOL
BEGIN
DECLARE x TINYINT UNSIGNED;
DECLARE l TINYINT UNSIGNED DEFAULT length(n);
DECLARE i TINYINT UNSIGNED DEFAULT l;
DECLARE s SMALLINT UNSIGNED DEFAULT 0;
WHILE i > 0 DO
SET x = mid(n,i,1);
IF (l-i) mod 2 = 1 THEN
SET x = x * 2;
END IF;
SET s = s + x div 10 + x mod 10;
SET i = i - 1;
END WHILE;
RETURN s != 0 && s mod 10 = 0;
END;
CREATE FUNCTION ccd (n TINYTEXT) RETURNS TINYINT
BEGIN
DECLARE x TINYINT UNSIGNED;
DECLARE l TINYINT UNSIGNED DEFAULT length(n);
DECLARE i TINYINT UNSIGNED DEFAULT l;
DECLARE s SMALLINT UNSIGNED DEFAULT 0;
WHILE i > 0 DO
SET x = mid(n,i,1);
IF (l-i) mod 2 = 0 THEN
SET x = x * 2;
END IF;
SET s = s + x div 10 + x mod 10;
SET i = i - 1;
END WHILE;
RETURN ceil(s/10)*10-s;
END;
Functions can then be used directly in SQL queries:
mysql> SELECT ccc(1234567890123452);
+-----------------------+
| ccc(1234567890123452) |
+-----------------------+
| 1 |
+-----------------------+
1 row in set (0.00 sec)
mysql> SELECT ccc(1234567890123451);
+-----------------------+
| ccc(1234567890123451) |
+-----------------------+
| 0 |
+-----------------------+
1 row in set (0.00 sec)
mysql> SELECT ccd(123456789012345);
+----------------------+
| ccd(123456789012345) |
+----------------------+
| 2 |
+----------------------+
1 row in set (0.00 sec)
mysql> SELECT ccd(234567890123451);
+----------------------+
| ccd(234567890123451) |
+----------------------+
| 1 |
+----------------------+
1 row in set (0.00 sec)
This is only to make sure that the numbers are valid using some basic RegEX patterns.
Note, this does not check to see if the numbers are in-use by someone.
http://www.roscripts.com/How_to_validate_credit_card_numbers-106.html
