_checkRequiredOptions example

            if ($config instanceof Zend_Config) {
                $config = $config->toArray();
            } else {
                /* * @see Zend_Db_Adapter_Exception */
                throw new Zend_Db_Adapter_Exception('Adapter parameters must be in an array or a Zend_Config object');
            }
        }

        $this->_checkRequiredOptions($config);

        $options = [
            Zend_Db::CASE_FOLDING => $this->_caseFolding,
            Zend_Db::AUTO_QUOTE_IDENTIFIERS => $this->_autoQuoteIdentifiers,
            Zend_Db::FETCH_MODE => $this->_fetchMode,
        ];
        $driverOptions = [];

        /* * normalize the config and merge it with the defaults */