Credit Card Identification and Validation Class - The credit_card class
provides methods for cleaning, validating and identifying the type of credit card numbers.

<?php 

class credit_card 
{ 
    function clean_no ($cc_no) 
    { 
        // Remove non-numeric characters from $cc_no   
        return ereg_replace ('[^0-9]+', '', $cc_no); 
    } 

    function identify ($cc_no) 
    { 
         $cc_no = credit_card::clean_no ($cc_no); 

        // Get card type based on prefix and length of card number   
        if (ereg ('^4(.{12}|.{15})$', $cc_no)) 
            return 'Visa';   
        if (ereg ('^5[1-5].{14}$', $cc_no)) 
            return 'Mastercard'; 
        if (ereg ('^3[47].{13}$', $cc_no)) 
            return 'American Express'; 
        if (ereg ('^3(0[0-5].{11}|[68].{12})$', $cc_no)) 
            return 'Diners Club/Carte Blanche'; 
        if (ereg ('^6011.{12}$', $cc_no)) 
            return 'Discover Card'; 
        if (ereg ('^(3.{15}|(2131|1800).{11})$', $cc_no)) 
            return 'JCB'; 
        if (ereg ('^2(014|149).{11})$', $cc_no)) 
            return 'enRoute'; 

        return 'unknown'; 
    } 

    function validate ($cc_no) 
    { 
        // Reverse and clean the number 
        $cc_no = strrev (credit_card::clean_no ($cc_no)); 
          
        // VALIDATION ALGORITHM 
        // Loop through the number one digit at a time 
        // Double the value of every second digit (starting from the right) 
        // Concatenate the new values with the unaffected digits 
        for ($ndx = 0; $ndx < strlen ($cc_no); ++$ndx) 
            $digits .= ($ndx % 2) ? $cc_no[$ndx] * 2 : $cc_no[$ndx]; 
          
        // Add all of the single digits together 
        for ($ndx = 0; $ndx < strlen ($digits); ++$ndx) 
            $sum += $digits[$ndx]; 

        // Valid card numbers will be transformed into a multiple of 10 
        return ($sum % 10) ? FALSE : TRUE; 
    } 

    function check ($cc_no) 
    { 
        $valid = credit_card::validate ($cc_no); 
        $type  = credit_card::identify ($cc_no); 
        return array ($valid, $type, 'valid' => $valid, 'type' => $type); 
    } 
} 

?>