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Credit Card Validation Script
Can anyone work out why this script is not working.
[code=php]
<?php # make sure these are the first two…
session_start(); # …lines in every file in the sequence!!!
foreach($_POST as $key => $value)
{
$_SESSION[$key] = $value;
}
?>
<html>
<head>
<?php
/*==============================================================================
This routine checks the credit card number. The following checks are made:
1. A number has been provided
2. The number is a right length for the card
3. The number has an appropriate prefix for the card
4. The number has a valid modulus 10 number check digit if required
If the validation fails an error is reported.
The structure of credit card formats was gleaned from
http://www.blackmarket-press.net/info/plastic/check_digit.htm
where the details of other cards may also be found.
Input parameters:
cardnumber number on the card
cardname name of card as defined in the card list below
Output parameters:
cardnumber number on the card
cardname name of card as defined in the card list below
Author: John Gardner
Date: 4th January 2005
Updated: 26th February 2005 additional credit cards added
==============================================================================*/
if (isset($_POST[‘submitted’]))
{
if (checkCreditCard ($_POST[‘CardNumber’], $_POST[‘CardType’], $ccerror, $ccerrortext))
{
$ccerrortext = ‘This card has a valid format’;
}
}
function checkCreditCard ($cardnumber, $cardname, &$errornumber, &$errortext) {
// Define the cards we support. You may add additional card types.
// Name: As in the selection box of the form – must be same as user’s
// Length: List of possible valid lengths of the card number for the card
// prefixes: List of possible prefixes for the card
// checkdigit Boolean to say whether there is a check digit
// Don’t forget – all but the last array definition needs a comma separator!
$cards = array ( array (‘name’ => ‘Visa’,
‘length’ => ‘13,16’,
‘prefixes’ => ‘4’,
‘checkdigit’ => true
),
array (‘name’ => ‘MasterCard’,
‘length’ => ’16’,
‘prefixes’ => ‘51,52,53,54,55’,
‘checkdigit’ => true
)
);
$ccErrorNo = 0;
$ccErrors [0] = “Unknown card type”;
$ccErrors [1] = “No card number provided”;
$ccErrors [2] = “Credit card number has invalid format”;
$ccErrors [3] = “Credit card number is invalid”;
$ccErrors [4] = “Credit card number is wrong length”;
// Establish card type
$cardType = -1;
for ($i=0; $i<sizeof($cards); $i++) {
// See if it is this card (ignoring the case of the string)
if (strtolower($cardname) == strtolower($cards[$i][‘name’])) {
$cardType = $i;
break;
}
}
// If card type not found, report an error
if ($cardType == -1) {
$errornumber = 0;
$errortext = $ccErrors [$errornumber];
return false;
}
// Ensure that the user has provided a credit card number
if (strlen($cardnumber) == 0) {
$errornumber = 1;
$errortext = $ccErrors [$errornumber];
return false;
}
// Check that the number is numeric, although we do permit a space to occur
// every four digits.
$cardexp = ‘^([0-9]{4})[[:space:]]?([0-9]{4})[[:space:]]?([0-9]{4})[[:space:]]?([0-9]{1,4})$’;
if (!ereg($cardexp,$cardnumber, $matches)) {
$errornumber = 2;
$errortext = $ccErrors [$errornumber];
return false;
}
// Now remove any spaces from the credit card number
$cardNo = $matches[1] . $matches[2] . $matches[3] . $matches[4];
// Now check the modulus 10 check digit – if required
if ($cards[$cardType][‘checkdigit’]) {
$checksum = 0; // running checksum total
$mychar = “”; // next char to process
$j = 1; // takes value of 1 or 2
// Process each digit one by one starting at the right
for ($i = strlen($cardNo) – 1; $i >= 0; $i–) {
// Extract the next digit and multiply by 1 or 2 on alternative digits.
$calc = $cardNo{$i} * $j;
// If the result is in two digits add 1 to the checksum total
if ($calc > 9) {
$checksum = $checksum + 1;
$calc = $calc – 10;
}
// Add the units element to the checksum total
$checksum = $checksum + $calc;
// Switch the value of j
if ($j ==1) {$j = 2;} else {$j = 1;};
}
// All done – if checksum is divisible by 10, it is a valid modulus 10.
// If not, report an error.
if ($checksum % 10 != 0) {
$errornumber = 3;
$errortext = $ccErrors [$errornumber];
return false;
}
}
// The following are the card-specific checks we undertake.
// Load an array with the valid prefixes for this card
$prefix = split(‘,’,$cards[$cardType][‘prefixes’]);
// Now see if any of them match what we have in the card number
$PrefixValid = false;
for ($i=0; $i<sizeof($prefix); $i++) {
$exp = ‘^’ . $prefix[$i];
if (ereg($exp,$cardNo)) {
$PrefixValid = true;
break;
}
}
// If it isn’t a valid prefix there’s no point at looking at the length
if (!$PrefixValid) {
$errornumber = 3;
$errortext = $ccErrors [$errornumber];
return false;
}
// See if the length is valid for this card
$LengthValid = false;
$lengths = split(‘,’,$cards[$cardType][‘length’]);
for ($j=0; $j<sizeof($lengths); $j++) {
if (strlen($cardNo) == $lengths[$j]) {
$LengthValid = true;
break;
}
}
// See if all is OK by seeing if the length was valid.
if (!$LengthValid) {
$errornumber = 4;
$errortext = $ccErrors [$errornumber];
return false;
};
// The credit card is in the required format.
return true;
}
/*============================================================================*/
?>
</head>
<body>
<form method=”POST” action=”<?php echo $_SESSION[‘PHP_SELF’] ?>”>
<table>
<tr>
<td width=”200″ align=”right”>
Card Type:
</td>
<td>
<select id=”cardname” name=”cardname” size=”1″ value=’$cardname’>
<option value=”Visa” <?php if(isset($_SESSION[‘cardname’]) && $_SESSION[‘cardname’] == ‘Visa’) { ?>selected=”selected”<? } ?>>Visa</option>
<option value=”Mastercard” <?php if(isset($_SESSION[‘cardname’]) && $_SESSION[‘cardname’] == ‘Mastercard’) { ?>selected=”selected”<? } ?>>Mastercard</option>
</select>
</td>
<td>
</td>
</tr>
<?php
echo “$error_cardname”;
?>
<tr>
<td>
</td>
<td align=”right”>
Card Number:
</td>
<td>
<?php
echo “<input type=”text” id=”cardnumber” name=”cardnumber” size=”20″ maxlength=”20″ title=”Please Enter the Card Number” value=’$cardnumber’ />”;
?>
</td>
<td>
</td>
</tr>
<?php
echo “$error_cardnumber”;
?>
</table>
<input type=”submit” name=”submitted” value=”submit”>
</form>
</body>
</html>
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