Why are these settings unregistered?
The error message is actually misleading here. WP isn’t checking if the settings are registered — e.g., if ( isset( $GLOBALS[‘wp_registered_settings’][‘foo’] ) ) — it’s checking if the form was posted to the default options page (options.php), rather than a custom one (options-general.php?page=foo). So, it’s entirely possible to get this warning after calling register_setting(), if … Read more