add_action('rss2_ns', function () {
echo 'xmlns:media="http://search.yahoo.com/mrss/"';
});
add_action('rss2_item', function () {
global $post;
if (has_post_thumbnail($post->ID)) {
$thumbnail_id = get_post_thumbnail_id($post->ID);
$thumbnail_url = wp_get_attachment_url($thumbnail_id);
echo '';
echo '';
}
});
