
Now I understand what you mean....
This is allowed in Phoca Gallery...
Phoca Gallery has two independent layers: Database layer and Filesystem layer... so if you add e.g. one image into the category, it will be added (database layer) and thumbnails will be created (filesystem layer) and if you will add the same image into the same category, it will be added as new image (with the same name but other id) because e.g. someone wants to have same images with other names, or someone will then move this image in some other category, or.... BUT the thumnails for this image are not more crated, so these two images (in database layer) are using only one image and its thumbnails (filesystem layer) and if you will e.g. move the image (database layer) into other category, the image (filesystem) will be still on the same place and it can be the source for the same images (database layer) in other categories (database layer)... so e.g. you have one image (filesystem) but 20 images (database) in 20 categories (database)
This works in case, if user select image and a category in select box
This doesn't work, if user select the category ... Then category will be added and all images in the category... if user will do the same after, nothing will be added... because it is ready for updating category:
E.g.: your folder is "new" and this folder have 10 images... you will add the into the gallery , all 10 images will be added (database layer)... if you will then upload next 15 images and you click on the category, only new 15 images will be added (updated to database layer) not all 25 images....
Jan