{
if (is_null($value)) {
return true;
}
$cardType = "";
$card_regexes = array(
"/^4\d{12}(\d\d\d){0,1}$/" => 'visa',
"/^5[12345]\d{14}$/" => 'mastercard',
"/^3[47]\d{13}$/" => 'amex',
"/^6011\d{12}$/" => 'discover',
"/^30[012345]\d{11}$/" => 'diners',
"/^3[68]\d{12}$/" => 'diners',
);
foreach ($card_regexes as $regex => $type) {
if (preg_match($regex, $value)) {
$cardType = $type;
break;
}
}
if ( ! $cardType) {
return false;
}
$revcode = strrev($value);
$checksum = 0;
for ($i = 0; $i < strlen($revcode); $i++) {
$currentNum = intval($revcode[$i]);
if ($i & 1) {
$currentNum *= 2;
}
$checksum += $currentNum % 10;
if ($currentNum > 9) {
$checksum += 1;
}
}
if ($checksum % 10 == 0) {
return true;
} else {
return false;
}
}