code: static protected function encode($number)
      {
          $k = self::$encoder;
          preg_match_all("/[1-9][0-9]|[0-9]/", $number, $a);
          $n = '';
          $o = count($k);
          foreach ($a[0] as $i) {
              if ($i < $o) {
                  $n .= $k[$i];
              } else {
                  $n .= '1' . $k[$i - $o];
              }
          }
          return $n;
      }
docs: Encodes an integer
  
  @param int $number integer to encode
  
  @return string encoded integer string