code: public function quoteValue($str)
      {
          if (!is_string($str)) {
              return $str;
          }
  
          if (($value = $this->db->getSlavePdo()->quote($str)) !== false) {
              return $value;
          }
  
          // the driver doesn't support quote (e.g. oci)
          return "'" . addcslashes(str_replace("'", "''", $str), "\000\n\r\\\032") . "'";
      }
docs: Quotes a string value for use in a query.
  Note that if the parameter is not a string, it will be returned without change.
  @param string $str string to be quoted
  @return string the properly quoted string
  @see https://secure.php.net/manual/en/function.PDO-quote.php