I have a relationship field displayed on certain posts and I want to populate it with articles only from a certain author ID.

I also want to run a meta_query to check an array of IDs, and if this array finds an ID matching the author ID, to include the articles associated with it:

    function reference_sort( $args, $field, $post_id ) {
        $author_id = get_post_field ('post_author', $post_id);
        $args['author']= $author_id;
        $args['post_type'] = 'reference_cases';
        $args['orderby'] = 'date';
        $args['order'] = 'DESC';
        $args['posts_per_page'] = 40;
        $args['meta_query'] = array(
            'relation' => 'OR',
            array(
                'key' => 'field_5f1ba9c9a725b',
                'value' => $author_id,
                'compare' => 'EXISTS',
            )
        );
        // return
        return $args;
    }
    add_filter('acf/fields/relationship/query/key=field_5f46f9c29272c', 'reference_sort', 10, 3);

Everything works apart from the meta_query which breaks everything.

I am using the EXISTS compare value because I assume it checks to see if the ID is in the key array.

Does anyone know why this isn’t working? It’s my first time using meta_query but it seems to be correct from what I can find.

Thanks