Append and Prepend to WordPress RSS Feed Content

The awesome part of RSS is that it lets you pull content wherever you want.  The bad part, as a publisher, is that the user may be missing out on important information that is on the site but doesn't display in articles.  WordPress' hook system to the rescue!

The PHP

We're going to hook onto the the_content and the_excerpt_rss function hooks to append or prepend content to feed entries:

// Additional RSS Content
$rss_more_content = 'blah blah blah';
$rss_more_position = 'before'; // or "after"

// Function which adds content to RSS entries
function add_rss_content($content) {
	global $rss_more_position, $rss_more_content;

	if(is_feed()) {
		if ($rss_more_position == 'before') {
			$content = "
$rss_more_content
\n$content";
		} else {
			$content .= "
$rss_more_content
\n";
		}
	}
	return $content;
}

// Add hooks
add_filter('the_content', 'add_rss_content');
add_filter('the_excerpt_rss', 'add_rss_content');

The only conditional is whether or not you want the content added at the top or bottom of the content block.  This function should go into your functions.php file, but how you pull in the additional content in is up to you!