通过ACF在wordpress中获取子站点的字段值

Question

We have a Wordpress website which has 10 sub sites(blogs) . We show the latest post of those sub sites on the main site . Recently we added and use Advanced Custom Field which is active now on the main site and all those 10 sub sites and in each one we sat just a true/false field and its name is : is_announce . In each site ( main or sub sites ) we have access to that field by get_field and it works great . The problem is , on the main site we have no access to those fields of sub sites.It seems get_field works good just for each site's scope ( main or sub sites )

How can we fix it ?

Addition : As i told you we show the latest post of each sub website . each one has been featured by one custom field ( is_announce ) . We want to read its value and if it is True , show something on the top of each post , something like tag .

Answer 1

Based on RST's comment , i could solve my problem :

                <?php

                        $slug = $post->blogname;
                        $blog_id = get_id_from_blogname($slug);

                        switch_to_blog($blog_id);

                        if( get_field('is_announce') )
                        {
                            echo "<div class='announce-container'>ANNOUNCE</div>";
                        }

                        restore_current_blog();

                ?>