I’m trying to figure out the best / most efficient way to populate several dropdowns on an archive page of a custom post type. The post type is images and the archive page obviously displays a list of images… each image has various custom fields such as author, area of research and instrumentation etc ( which act a little like taxonomies but are actually other custom post types ).
What I want to do is populate some drop downs to act as front end filter options with unique arrays ( no repeats ) for all the values of each custom field attached to the image post types. The querying / filtering / url get value functionality is all sorted. I just want a neat way of populating these drop downs.
I could of course call WP_Query to fetch all the images post type data and loop through building arrays of custom fields, then calling array_unique and then looping back through to populate the selects. However, I feel this is way too much php processes and possibly overkill, especially considering I then need to the for main loop to build the page as well.
Another way would be to call WP_Query on the filtering post types ( author, area of research and instrumentation etc ) and do it that way, but then there might be some of these that are not attached to any images.
Is there any neat acf or wordpress functions that I don’t yet know of yet to achieve something like this?
