Algorithm to get the excel-like column name of a number

Question

I\'m working on a script that generate some Excel documents and I need to convert a number into its column name equivalent. For example:

1 => A
2 => B
         


        

Answer 1

Combining ircmaxell's recursive answer I've got this one:

    function getNameFromNumber($num, $index=0) {
        $index = abs($index*1); //make sure index is a positive integer
        $numeric = ($num - $index) % 26; 
        $letter = chr(65 + $numeric);
        $num2 = intval(($num -$index) / 26);
        if ($num2 > 0) {
            return getNameFromNumber($num2 - 1 + $index) . $letter;
        } else {
            return $letter;
        }
    }

I'm using the default indexing as 0 based, but it can be any positive integer for when juggling with arrays in PHP.