function rss_post_thumbnail($content) {
global $post;
if(has_post_thumbnail($post->ID)) {
$content = '<p>' . get_the_post_thumbnail($post->ID) .
'</p>' . get_the_content();
}
return $content;
}
add_filter('the_excerpt_rss', 'rss_post_thumbnail');
add_filter('the_content_feed', 'rss_post_thumbnail');

http://www.wpbeginner.com/wp-tutorials/25-extremely-useful-tricks-for-the-wordpress-functions-file/

Code in functions.php einfügen

Post Thumbnails im RSS Feed aktivieren

post, wordpress

PHP