foreach ( $gateway->form_fields as $key => $field ) {
                if ( isset( $request['settings'][ $key ] ) ) {
                    if ( is_callable( array( $this, 'validate_setting_' . $field['type'] . '_field' ) ) ) {
                        $value = $this->{'validate_setting_' . $field['type'] . '_field'}( $request['settings'][ $key ], $field );
                    } else {