how to repair undefined array key widget_classic_editor

To repair an undefined array key for "widget_classic_editor" specifically, you would need to know the context in which this key is being used and BY DOWNGRADING THE PHP VERSION TO 7.4 for those who are using themes that not supported by latest PHP version.

If this key is being used in the context of a WordPress theme or plugin that uses the Classic Editor widget, you may need to check the settings or configuration of the theme or plugin to ensure that the widget is properly registered and the key is defined.

If you are encountering this issue in a custom WordPress plugin or theme that you are developing, you can register the widget using register_widget() function in your functions.php file, or in a separate file that's included in your theme.

class Classic_Editor_Widget extends WP_Widget {
    ...
}

add_action( 'widgets_init', 'register_classic_editor_widget' );
function register_classic_editor_widget() {
    register_widget( 'Classic_Editor_Widget' );
}

Another possible cause of this issue could be that the widget was deactivated or removed in the WordPress backend. In this case, you may need to activate the widget or re-install the plugin/theme that provides this widget.

If you can give me more information about your specific use case and the error message you are seeing, I can provide more specific guidance on how to repair the undefined array key for "widget_classic_editor".