Is there any action filter/hook for validating a custom field before publishing the post?
At the beginning of wp_insert_post, the function that saves/updates a post, there is a filter called wp_insert_post_empty_content. By default this filter checks whether the title, editor, and excerpt fields are all empty, in which case the save process will be halted. However, since all the fields to be saved are passed to this filter, you … Read more