Value
Constants::CALLBACK_TYPE_MODAL = 0
Semantics
Every action callback returns array( $callback_type, $payload ) from execute_callback(). With CALLBACK_TYPE_MODAL:
The payload is rendered modal HTML. The dispatcher wraps it in a wrModalObject.showNewModal(...) call, so the frontend opens (or replaces) a modal with the returned content. Script blocks inside the modal body are JSON-escaped (JSON_HEX_TAG) so embedded </script> sequences cannot break the outer script tag.
Typical usage
Rendering forms, entry views, history views — everything that opens in a dialog.
public function execute_callback(): array {
return array( Constants::CALLBACK_TYPE_MODAL, $payload );
}