Programming PHP

Example 4-1. Credit-card validator (continued)
function IsValidCreditCard($inCardNumber, $inCardType) {
// Assume it's okay
$isValid = true;
// Strip all non-numbers from the string
$inCardNumber = ereg_replace('[^[:digit:]]','', $inCardNumber);
// Make sure the card number and type match
switch($inCardType) {
case 'mastercard':
$isValid = ereg('^5[1-5].{14}$', $inCardNumber);
break;
}
case 'visa':
$isValid = ereg('^4.{15}$|^4.{12}$', $inCardNumber);
break;
case 'amex':
$isValid = ereg('^3[47].{13}$', $inCardNumber);
break;
case 'discover':
$isValid = ereg('^6011.{12}$', $inCardNumber);
break;
case 'diners':
$isValid = ereg('^30[0-5].{11}$|^3[68].{12}$', $inCardNumber);
break;
case 'jcb':
$isValid = ereg('^3.{15}$|^2131|1800.{11}$', $inCardNumber);
break;
// It passed the rudimentary test; let's check it against the Luhn this time
if($isValid) {
// Work in reverse
$inCardNumber = strrev($inCardNumber);
// Total the digits in the number, doubling those in odd-numbered positions
$theTotal = 0;
for ($i = 0; $i < strlen($inCardNumber); $i++) {
$theAdder = (int) $inCardNumber{$i};
// Double the numbers in odd-numbered positions
if($i % 2) {
$theAdder 9) { $theAdder -= 9; }
}
$theTotal += $theAdder;
}
102 | Chapter 4: Strings
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