voravor

@terriz Yes, sorry about that. Here’s a corrected version:

add_filter('instant_articles_transformed_element', 'my_subtitle', 10, 1);

//the filter is provided by the fb-instant-articles plugin
//it passes in the instant_article object, which you can modify
//before it finishes rendering the feed.
function my_subtitle($article) {
    global $post;
    $my_subtitle = get_the_excerpt(); //replace this with whatever

    //the instant article has a Header element, which has a subtitle property.
   //Get it and add a subtitle
    $subtitle = $article->getHeader()->withSubTitle($my_subtitle);

    //return the modified instant article back into the render flow
    return $article;

   //verify that your /feed/instant-articles contains <h2>'s in each feed item <content> elements.
}

Here’s how I solved this type of thing, although it’s assuredly roundabout.

FYI: Transform rules are the correct way to go, but the docs are paleolithic. Wait a bit until the platform/docs/priorities stabilize. In theory, transforms allow you to replace *any* markup with *any* instant articles element.

Try using this filter in your functions.php to add a subtitle to the instant article.

add_filter('instant_articles_transformed_element', 'my_subtitle'], 10, 1);

//the filter is provided by the fb-instant-articles plugin
//it passes in the instant_article object, which you can modify
//before it finishes rendering the feed.
function my_subtitle($article) {
    global $post;
    $my_subtitle = get_the_excerpt(); //replace this with whatever

    //the instant article has a Header element, which has a subtitle property.
   //Get it and add a subtitle
    $subtitle = $article->getHeader()->withSubTitle($my_subtitle);

    //return the modified instant article back into the render flow
    return $article;

   //verify that your /feed/instant-articles contains <h2>'s in each feed item <content> elements.
}