Wordpress RSS 2.0 image enclosure

function feedFilter($query) {
	if ($query->is_feed) {
		add_filter('rss2_item', 'feedContentFilter');
		}
	return $query;
}
add_filter('pre_get_posts','feedFilter');
 
function feedContentFilter($item) {
	
	global $post;
	
	$args = array(
		'order'          => 'ASC',
		'post_type'      => 'attachment',
		'post_parent'    => $post->ID,
		'post_mime_type' => 'image',
		'post_status'    => null,
		'numberposts'    => 1,
	);
	$attachments = get_posts($args);
	if ($attachments) {
		foreach ($attachments as $attachment) {
			$image = wp_get_attachment_image_src($attachment->ID, 'large');
			$mime = get_post_mime_type($attachment->ID);
		}
	}

	if ($image) {
		echo '<enclosure url="'.$image[0].'" length="" type="'.$mime.'"/>';
	} 
	return $item;
}