code: public static function isValidFopType($fopType)
      {
          return ($fopType == self::IDENT_CASH
              || $fopType == self::IDENT_CHECK
              || $fopType == self::IDENT_CREDITCARD
              || $fopType == self::IDENT_MISC);
      }
docs: Check if the given Form Of Payment type is valid
  
  @param string $fopType
  @return boolean