code: public static function get($length = 8, $outputFormat = Code::FORMAT_ALNUM)
      {
          static::throwUnlessAcceptable($outputFormat, $length);
  
          $number = rand(100, 900) . str_replace('.', '', microtime(true));
          $output = self::convertBase($number, self::FORMAT_NUMBER, $outputFormat);
  
          if(strlen($output) < $length) {
              $output .= substr(str_shuffle($outputFormat.$outputFormat), 0, ($length - strlen($output)));
          }
          if(strlen($output) > $length) {
              $output = substr($output, 0, $length);
          }
  
          return $output;
      }
docs: Get a random code of fixed length.
  
  @param int $length  length of code, default 8
  @param string $outputFormat One of Code::FORMAT_* constants. Default Code::FORMAT_ALNUM
  
  @return string