Generating Luhn Checksums

Question

There are lots of implementations for validating Luhn checksums but very few for generating them. I\'ve come across this one however in my tests it has revealed to be buggy

Answer 1

your php is buggy, it leads into an infinite loop. This is the working version that I'm using, modified from your code

function Luhn($number) {

$stack = 0;
$number = str_split(strrev($number));

foreach ($number as $key => $value)
{
    if ($key % 2 == 0)
    {
        $value = array_sum(str_split($value * 2));
    }
    $stack += $value;
}
$stack %= 10;

if ($stack != 0)
{
    $stack -= 10;     $stack = abs($stack);
}


$number = implode('', array_reverse($number));
$number = $number . strval($stack);

return $number; 

}

Create a php and run in your localhost Luhn(xxxxxxxx) to confirm.