thumbnail in WordPress feed

// put this into functions.php

add_filter('the_excerpt_rss','rss_filter') ;
add_filter('the_content_feed','rss_filter_full') ;
function rss_filter($content){
  global $post;
    $thumbId = get_post_thumbnail_id();
    if($thumbId) {
    $img = wp_get_attachment_image_src($thumbId, 'large');
    return '<img src="'.$img[0].'" alt="'.$post->post_excerpt.' title="'.$post->post_excerpt.'""/>'.$content;
  }
}

function rss_filter_full($content){
  global $post;
    $thumbId = get_post_thumbnail_id();
    if($thumbId) {
    $img = wp_get_attachment_image_src($thumbId, 'large');
    return '<img src="'.$img[0].'" alt="'.$post->post_excerpt.'" title="'.$post->post_excerpt.'"/>'.$content;
  }
}