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.
There are three parts to the validation of the card number:
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 ($total % 10 == 0) ? TRUE : FALSE;
}
?>
From 10 regular expressions you can't live without in PHP:
function check_cc($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:
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.
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