code: public function isValidType($type)
      {
          return in_array($type, array(
              self::ANY,
              self::FIXED_LINE,
              self::MOBILE,
              self::PAGER,
              self::PERSONAL_NUMBER,
              self::PREMIUM_RATE,
              self::SHARED_COST,
              self::TOLL_FREE,
              self::UAN,
              self::VOIP,
              self::VOICEMAIL,
          ), true);
      }
docs: Returns whether the given type is valid.
  
  @param string $type
  
  @return bool