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File: Luhn.php

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  Classes of Rolands Kusins  >  PHP Luhn Algorithm  >  Luhn.php  >  Download  
File: Luhn.php
Role: Class source
Content type: text/plain
Description: Luhn check digit calculation class
Class: PHP Luhn Algorithm
Calculate and validate a Luhn check digit
Author: By
Last change: New calculation algorithm, see
http://www.phpclasses.org/discuss/package/8471/thread/1/
Date: 1 year ago
Size: 2,203 bytes
 

Contents

Class file image Download
<?php
/**
 * Luhn algorithm (a.k.a. modulus 10) is a simple formula used to validate variety of identification numbers.
 * It is not intended to be a cyrptographically secure hash function, it was designed to protect against accidental errors.
 * See http://en.wikipedia.org/wiki/Luhn_algorithm
 *
 * @author Rolands Kusiņš
 * @version 0.2
 * @license GPL
 */
class Luhn{
    private
$sumTable = array(array(0,1,2,3,4,5,6,7,8,9),array(0,2,4,6,8,1,3,5,7,9));
   
/**
     * Calculate check digit according to Luhn's algorithm
     * New method (suggested by H.Johnson), see http://www.phpclasses.org/discuss/package/8471/thread/1/
     *
     * @param string $number
     * @return integer
     */
   
public function calculate($number){
       
$length = strlen($number);
       
$sum = 0;
       
$flip = 1;
       
// Sum digits (last one is check digit, which is not in parameter)
       
for($i=$length-1;$i>=0;--$i) $sum += $this->sumTable[$flip++ & 0x1][$number[$i]];
       
// Multiply by 9
       
$sum *= 9;
       
// Last digit of sum is check digit
       
return (int)substr($sum,-1,1);
    }
   
   
/**
     * Calculate check digit according to Luhn's algorithm
     * This is an old method, tests show that this is little bit slower than new one
     *
     * @param string $number
     * @return integer
     */
   
public function calculateOld($number){
       
$length = strlen($number);
       
$sum = 0;
       
$p = $length % 2;
       
// Sum digits, where every second digit from right is doubled (last one is check digit, which is not in parameter)
       
for($i=$length-1;$i>=0;--$i){
           
$digit = $number[$i];
           
// Every second digit is doubled
           
if($i % 2 != $p){
               
$digit *= 2;
               
// If doubled value is 10 or more (for example 13), then add to sum each digit (i.e. 1 and 3)
               
if($digit > 9){
                   
$sum += $digit[0];
                   
$sum += $digit[1];
                } else{
                   
$sum += $digit;
                }
            } else{
               
$sum += $digit;
            }
        }
       
// Multiply by 9
       
$sum *= 9;
       
// Last one is check digit
       
return (int)substr($sum,-1,1);
    }
   
   
/**
     * Validate number against check digit
     *
     * @param string $number
     * @param integer $digit
     * @return boolean
     */
   
public function validate($number,$digit){
       
$calculated = $this->calculate($number);
        if(
$digit == $calculated) return true;
        else return
false;
    }
}
?>