Demo for Luhn algorithm in PHP

javier — Fri, 24 Feb 2006 18:30:26 +0000

If you have a number that adheres to the Luhn algorithm for validation, you may check it easily with this short PHP snippet.

function luhn($str) {

        $odd = !strlen($str)%2;

        $sum = 0;

        for($i=0;$i<strlen($str);++$i) {

            $n=0+$str[$i];

            $odd=!$odd;

            if($odd) {

                $sum+=$n;

            } else {

                $x=2*$n;

                $sum+=$x>9?$x-9:$x;

            }

        }

        return(($sum%10)==0);

}

$num = $_GET[‘number’];

?>

Online Luhn algorithm test

 if($num) { ?>

if(luhn($num)){?>

htmlspecialchars($num)?> is valid

}else{?>

htmlspecialchars($num)?> is NOT valid

   } ?>

 } ?>

Number: urlencode($num)?>" size="40"/>

(Download)
You may test this script at http://javier.rodriguez.org.mx/code/luhn-test.php.
Please consider that this is a demo, so please do not use this to check credit card numbers unless you send me an expiry date. CCV2 has taken over as the preferred method for credit card number validation anyway.

Luhn algorithm in PHP

javier — Mon, 26 Dec 2005 14:53:03 +0000

As I mentioned before, the Luhn algorithm is used to validate some interesting numbers, most notably GSM IMEIs and credit card numbers. Here’s another implementation I wrote, this time in PHP.

function luhn($str) {

                $odd = !strlen($str)%2;

                $sum = 0;

                for($i=0;$i<strlen($str);++$i) {

                        $n=0+$str[$i];

                        $odd=!$odd;

                        if($odd) {

                                $sum+=$n;

                        } else {

                                $x=2*$n;

                                $sum+=$x>9?$x-9:$x;

                        }

                }

                return(($sum%10)==0);

        }

(Download)

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Demo for Luhn algorithm in PHP

Luhn algorithm in PHP