2010/1/5 Richard Quadling <rquadl...@googlemail.com>:
> 2010/1/5 Angus Mann <angusm...@pobox.com>:
>> Hi all. Perhaps a lazy request, but does anybody have some cut-n-paste code
>> to calculate a Luhn check-digit?
>>
>> It's a check-digit often added to the end of things like credit card or
>> account numbers to make detecting typo's a bit easier.
>>
>> I found lots of code to validate a number once the check-digit is applied,
>> but nothing to calculate the digit in the first place.
>>
>> Thanks in advance !
>> Angus
>>
>>
>
> Modified version found at
> http://blog.planzero.org/2009/08/luhn-modulus-implementation-php/
>
> <?php
> /* Luhn algorithm number checker - (c) 2005-2008 - planzero.org *
> * This code has been released into the public domain, however please *
> * give credit to the original author where possible. */
>
> function luhn_check($number) {
> // If the total mod 10 equals 0, the number is valid
> return (luhn_process($number) % 10 == 0) ? TRUE : FALSE;
>
> }
>
> function luhn_process($number) {
>
> // Strip any non-digits (useful for credit card numbers with spaces
> and hyphens)
> $number=preg_replace('/\D/', '', $number);
>
> // Set the string length and parity
> $number_length=strlen($number);
> $parity=$number_length % 2;
>
> // Loop through each digit and do the maths
> $total=0;
> for ($i=0; $i<$number_length; $i++) {
> $digit=$number[$i];
> // Multiply alternate digits by two
> if ($i % 2 == $parity) {
> $digit*=2;
> // If the sum is two digits, add them together (in effect)
> if ($digit > 9) {
> $digit-=9;
> }
> }
> // Total up the digits
> $total+=$digit;
> }
>
> return $total;
> }
>
> function luhn_checkdigit($number) {
> return 10 - (luhn_process($number . '0') % 20);
> }
>
>
> echo '49927398716 is ', (luhn_check('49927398716') ? 'Valid' :
> 'Invalid'), PHP_EOL;
> echo 'The check digit for 4992739871 is ',
> luhn_checkdigit('4992739871'), PHP_EOL;
> ?>
>
>
> outputs ...
>
> 49927398716 is Valid
> The check digit for 4992739871 is 6
>
>
>
> --
> -----
> Richard Quadling
> "Standing on the shoulders of some very clever giants!"
> EE : http://www.experts-exchange.com/M_248814.html
> Zend Certified Engineer : http://zend.com/zce.php?c=ZEND002498&r=213474731
> ZOPA : http://uk.zopa.com/member/RQuadling
>
And that 20 is a typo. Sorry.
function luhn_checkdigit($number) {
return 10 - (luhn_process($number . '0') % 10);
}
--
-----
Richard Quadling
"Standing on the shoulders of some very clever giants!"
EE : http://www.experts-exchange.com/M_248814.html
Zend Certified Engineer : http://zend.com/zce.php?c=ZEND002498&r=213474731
ZOPA : http://uk.zopa.com/member/RQuadling
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