Add featured image to RSS Feed

featured-image-to-rss.php

<?php
/**
 * Adds a featured image to RSS feeds.
 *
 * @param string $content The content of the post.
 * @return string Modified content with featured image.
 */
function prefix_featured_to_rss( $content ) {
    global $post;

    if ( has_post_thumbnail( $post->ID ) ) {
        $thumbnail = get_the_post_thumbnail( $post->ID, 'large', array( 'style' => 'margin-bottom: 15px;' ) );
      
        $content = '<div>' . $thumbnail . '</div>' . $content;
    }

    return $content;
}
 
add_filter( 'the_excerpt_rss', 'prefix_featured_to_rss' );
add_filter( 'the_content_feed', 'prefix_featured_to_rss' );