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//Function to add featured image in RSS feeds
function featured_image_in_rss($content)
{
  // Global $post variable global $post;
  // Check if the post has a featured image
  if (has_post_thumbnail($post->ID))
  {
    $content = get_the_post_thumbnail($post->ID, 'full', array('style' => 'margin-bottom:10px;')) . $content;
    
  } 
  
  return $content;
  
} 

//Add the filter for RSS feeds Excerpt
add_filter('the_excerpt_rss', 'featured_image_in_rss');

//Add the filter for RSS feed content
add_filter('the_content_feed', 'featured_image_in_rss');