I am using advanced custom fields repeater-field to get the image url like this:
<?php the_sub_field('billede'); ?>
But I also want to get the attachment ID for the image, to be used for something else.
Is this possible? :)
The simplest way to do this is to change your field to return attachment ID instead of URL, and then when you need the URL, use
wp_get_attachment_image_src with the ID. The only method I'm aware of to get ID from URL is with a custom SQL query.