public static function decimalToAlphanumeric($number, $base = 64, $index = false)
    {
        if (!$base) {
            $base = strlen($index);
        } elseif (!$index) {
            $index = substr("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ", 0, $base);
        }

        $out = "";

        for ($i = floor(log10($number) / log10($base)); $i >= 0; $i--) { 
            $no = floor($num/pow($base, $i));
            $out = $out.substr($index, $no, 1);
            $number = $number - ($no * pow($base, $i));
        }
        return $out;
    }