this is what is returned in $field
Array ( [ID] => 0 [key] => field_5a47128676459 [label] => Utilisateur [name] => acf[field_5a47128676459] [prefix] => acf [type] => user [value] => [menu_order] => 0 [instructions] => [required] => 0 [id] => acf-field_5a47128676459 [class] => [conditional_logic] => 0 [parent] => group_5a471067bee5c [wrapper] => Array ( [width] => [class] => [id] => ) [role] => [allow_null] => 0 [multiple] => 0 [return_format] => id [_name] => _user_id [_valid] => 1 [_prepare] => 1 )
