When I use setFieldUpload, strangely, the first path must use $_SERVER['DOCUMENT_ROOT'], and the second path, which is the same no.
I guess it's because I'm not a very good connoisseur of PHP subtlety. But this can help others to not spend hours, surely.
crud->setFieldUpload('photo1', $_SERVER['DOCUMENT_ROOT']'/assets/images/accueil/photo1','/assets/images/accueil/accueil/photo1') ;