How to add post featured image to RSS item tag?

I am able to add a post featured image to the RSS feed like so:

function insertThumbnailRSS($content) {
    global $post;
    if(has_post_thumbnail($post->ID)){
        $content = ''.get_the_post_thumbnail($post->ID, 'thumbnail', array('alt' => get_the_title(), 'title' => get_the_title(), 'style' => 'float:right;')).''.$content;
    }
    return $content;
}
add_filter('the_excerpt_rss', 'insertThumbnailRSS');
add_filter('the_content_feed', 'insertThumbnailRSS');

However, upon examining the XML generated for the RSS feed, I noticed it sticks the featured image into the XML description item tag.

How can I insert post featured image into it’s own RSS feed item tag of let’s say “image”, rather than just inserting it in with the post’s content?

Answers:

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Method 1

You could do it by adding an action to the hook ‘rss2_item’ like so:

add_action('rss2_item', function(){
  global $post;

  $output = '';
  $thumbnail_ID = get_post_thumbnail_id( $post->ID );
  $thumbnail = wp_get_attachment_image_src($thumbnail_ID, 'thumbnail');
  $output .= '<post-thumbnail>';
    $output .= '<url>'. $thumbnail[0] .'</url>';
    $output .= '<width>'. $thumbnail[1] .'</width>';
    $output .= '<height>'. $thumbnail[2] .'</height>';
    $output .= '</post-thumbnail>';

  echo $output;
});

Method 2

Building off of codekipple’s great answer, here’s my modified implementation, which uses the valid Media RSS element media:content element (spec) and checking for the existence of a thumbnail/featured image:

    function dn_add_rss_image() {
        global $post;

        $output = '';
        if ( has_post_thumbnail( $post->ID ) ) {
            $thumbnail_ID = get_post_thumbnail_id( $post->ID );
            $thumbnail = wp_get_attachment_image_src( $thumbnail_ID, 'thumbnail' );

            $output .= '<media:content xmlns:media="http://search.yahoo.com/mrss/" medium="image" type="image/jpeg"';
            $output .= ' url="'. $thumbnail[0] .'"';
            $output .= ' width="'. $thumbnail[1] .'"';
            $output .= ' height="'. $thumbnail[2] .'"';
            $output .= ' />';
        }
        echo $output;
    }
    add_action( 'rss2_item', 'dn_add_rss_image' );

Note: Include the xmlns attribute here to make it validate. WordPress’s initial install doesn’t include that namespace declaration, and while you can change it, so can other themes/plugins.

More details on the other attributes etc. are in my non-WordPress-specific answer here.

This integrates with MailChimp’s RSS newsletter building.

Method 3

Building off codekipple and D_N, I wanted a few more attributes in my media:content so here’s what I did:

function add_media_content_to_feed() {
  global $post;

  $post_id = $post->ID;

  if(!has_post_thumbnail($post)) {
    return;
  }

  $thumbnail_size = 'large';
  $thumbnail_id   = get_post_thumbnail_id($post_id);

  $file           = image_get_intermediate_size(get_post_thumbnail_id(), $thumbnail_size);

  $url            = $file['url'];
  $type           = $file['mime-type'];
  $height         = $file['height'];
  $width          = $file['width'];
  $file_size      = '';

  $path           = $file['path'];
  if($path && 0 !== strpos($path, '/') && !preg_match('|^.:\|', $path) && (($uploads = wp_get_upload_dir()) && false === $uploads['error'])) {
    $path         = $uploads['basedir']."/$path";
    $file_size    = filesize($path);
  }

  echo sprintf(__('<media:content url="%s" type="%s" medium="image" height="%s" width="%s" fileSize="%s" />'),
    $url,
    $type,
    $height,
    $width,
    $file_size
  );

}
add_action('rss2_item', 'add_media_content_to_feed');

codekipple’s answer also actually adds the image below all feed content. I wanted my image above content, so I did this:

function add_featured_image_to_feed($content, $feed_type) {
  global $post;
  $post_id = $post->ID;
  if(has_post_thumbnail($post)) {
    $content = '<div class="feed-image">'.get_the_post_thumbnail($post_id, 'large').'</div>'.$content;
  }
  return $content;
}
add_filter('the_content_feed', 'add_featured_image_to_feed', 10, 9999);

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0