<?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 a variety of sources on 

the web, although the best is probably on Wikepedia ("Credit card number"):


  http://en.wikipedia.org/wiki/Credit_card_number


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

            1st July 2006       multiple definition of Discovery card removed

            27th Nov. 2006      Additional cards added from Wikipedia

						8th Dec 2007				Problem with Solo card definition corrected

						18th Jan 2008				Support for 18 digit Maestro cards added

            26th Nov 2008       Support for 19 digit Maestro cards added

            19th June 2009      Support for Laser debit cards

						
if (isset($_GET['submitted'])) {

  if (checkCreditCard ($_GET['CardNumber'], $_GET['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' => 'American Express', 

                          'length' => '15', 

                          'prefixes' => '34,37',

                          'checkdigit' => true

                         ),

                   array ('name' => 'Diners Club Carte Blanche', 

                          'length' => '14', 

                          'prefixes' => '300,301,302,303,304,305',

                          'checkdigit' => true

                         ),

                   array ('name' => 'Diners Club', 

                          'length' => '14,16',

                          'prefixes' => '305,36,38,54,55',

                          'checkdigit' => true

                         ),

                   array ('name' => 'Discover', 

                          'length' => '16', 

                          'prefixes' => '6011,622,64,65',

                          'checkdigit' => true

                         ),

                   array ('name' => 'Diners Club Enroute', 

                          'length' => '15', 

                          'prefixes' => '2014,2149',

                          'checkdigit' => true

                         ),

                   array ('name' => 'JCB', 

                          'length' => '16', 

                          'prefixes' => '35',

                          'checkdigit' => true

                         ),

                   array ('name' => 'Maestro', 

                          'length' => '12,13,14,15,16,18,19', 

                          'prefixes' => '5018,5020,5038,6304,6759,6761',

                          'checkdigit' => true

                         ),

                   array ('name' => 'MasterCard', 

                          'length' => '16', 

                          'prefixes' => '51,52,53,54,55',

                          'checkdigit' => true

                         ),

                   array ('name' => 'Solo', 

                          'length' => '16,18,19', 

                          'prefixes' => '6334,6767',

                          'checkdigit' => true

                         ),

                   array ('name' => 'Switch', 

                          'length' => '16,18,19', 

                          'prefixes' => '4903,4905,4911,4936,564182,633110,6333,6759',

                          'checkdigit' => true

                         ),

                   array ('name' => 'Visa', 

                          'length' => '13,16', 

                          'prefixes' => '4',

                          'checkdigit' => true

                         ),

                   array ('name' => 'Visa Electron', 

                          'length' => '16', 

                          'prefixes' => '417500,4917,4913,4508,4844',

                          'checkdigit' => true

                         ),

                   array ('name' => 'LaserCard', 

                          'length' => '16,17,18,19', 

                          'prefixes' => '6304,6706,6771,6709',

                          '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; 

  }

  
  // Remove any spaces from the credit card number

  $cardNo = str_replace (' ', '', $cardnumber);  

   
  // Check that the number is numeric and of the right sort of length.

  if (!preg_match('/^[0-9]{13,19}$/i',$cardNo))  {

     $errornumber = 2;     

     $errortext = $ccErrors [$errornumber];

     return false; 

  }

       
  // 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

  $prefix = explode(',',$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 (preg_match('/'.$exp.'/',$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;

  $lengths = explode(',',$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;

}

/*============================================================================*/

?>