2010/1/5 Richard Quadling <rquadling [at] googlemail.com>:
> 2010/1/5 Angus Mann <angusmann [at] pobox.com>:
>> Hi all. Perhaps a lazy request, but does anybody have some cut-n-paste c=
ode 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 applie=
d, 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 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0*
> =C2=A0* This code has been released into the public domain, however pleas=
e =C2=A0 =C2=A0 =C2=A0*
> =C2=A0* give credit to the original author where possible. =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0*/
>
> function luhn_check($number) {
> =C2=A0// If the total mod 10 equals 0, the number is valid
> =C2=A0return (luhn_process($number) % 10 =3D=3D 0) ? TRUE : FALSE;
>
> }
>
> function luhn_process($number) {
>
> =C2=A0// Strip any non-digits (useful for credit card numbers with spaces
> and hyphens)
> =C2=A0$number=3Dpreg_replace('/\D/', '', $number);
>
> =C2=A0// Set the string length and parity
> =C2=A0$number_length=3Dstrlen($number);
> =C2=A0$parity=3D$number_length % 2;
>
> =C2=A0// Loop through each digit and do the maths
> =C2=A0$total=3D0;
> =C2=A0for ($i=3D0; $i<$number_length; $i++) {
> =C2=A0 =C2=A0$digit=3D$number[$i];
> =C2=A0 =C2=A0// Multiply alternate digits by two
> =C2=A0 =C2=A0if ($i % 2 =3D=3D $parity) {
> =C2=A0 =C2=A0 =C2=A0$digit*=3D2;
> =C2=A0 =C2=A0 =C2=A0// If the sum is two digits, add them together (in ef=
fect)
> =C2=A0 =C2=A0 =C2=A0if ($digit > 9) {
> =C2=A0 =C2=A0 =C2=A0 =C2=A0$digit-=3D9;
> =C2=A0 =C2=A0 =C2=A0}
> =C2=A0 =C2=A0}
> =C2=A0 =C2=A0// Total up the digits
> =C2=A0 =C2=A0$total+=3D$digit;
> =C2=A0}
>
> =C2=A0return $total;
> }
>
> function luhn_checkdigit($number) {
> =C2=A0return 10 - (luhn_process($number . '0') % 20);
> }
>
>
> echo '49927398716 is ', (luhn_check('49927398716') ? 'Valid' :
> 'Invalid'), PHP_EOL;
> echo 'The check digit for 4992739871 is ',
> luhn_checkdigit('4992739871'), PHP_EOL;
> ?>
>
>
> outputs ...
>
> 49927398716 is Valid
> The check digit for 4992739871 is 6
>
>
>
> --
> -----
> Richard Quadling
> "Standing on the shoulders of some very clever giants!"
> EE : http://www.experts-exchange.com/M_248814.html
> Zend Certified Engineer : http://zend.com/zce.php?c=3DZEND002498&r=3D2134=
74731
> ZOPA : http://uk.zopa.com/member/RQuadling
>
And that 20 is a typo. Sorry.
function luhn_checkdigit($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=3DZEND002498&r=3D213474=
731
ZOPA : http://uk.zopa.com/member/RQuadling
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