The goal of this rewrite was to get a RSS fedd with the 15 last posts, with the content of the message, to allow user to read the entire forum from a RSS Reader. This script use the image from the icons hack.

According to the license of punbb the following idea and code are subject to the GPL.

http://forum.swisslinux.org/extern.php?action=new&type=rss

Edit extern.php, and write put between :

	// Should we output this as RSS?
... and 
	// Output regular HTML 

those lines :

// ***** BEGIN rewritten by fbianco for Swisslinux.org *****//
	if (isset($_GET['type']) && strtoupper($_GET['type']) == 'RSS')
	{
		$rss_description = ($_GET['action'] == 'active') ? $lang_common['RSS Desc Active'] : $lang_common['RSS Desc New'];
		$url_action = ($_GET['action'] == 'active') ? '&action=new' : '';
 
		// Send header rss+xml, encoding and no cache
		header('Content-Type: application/rss+xml; charset=UTF-8');
		header('Expires: '.gmdate('D, d M Y H:i:s').' GMT');
		header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
		header('Pragma: public');
 
		// It's time for some syndication! rss 2.0 valid output !
		echo '<?xml version="1.0" encoding="'.$lang_common['lang_encoding'].'"?>'."\r\n";
		echo '<rss version="2.0">'."\r\n";
		echo '<channel>'."\r\n";
		echo "\t".'<title>'.pun_htmlspecialchars($pun_config['o_board_title']).'</title>'."\r\n";
		echo "\t".'<link>'.$pun_config['o_base_url'].'/</link>'."\r\n";
		echo "\t".'<description>'.pun_htmlspecialchars($rss_description.' '.$pun_config['o_board_title']).'</description>'."\r\n";
		echo "\t".'<language>en-us</language>'."\r\n";
 
		// *** Added for Swisslinux.org ***** //
		echo "\t".'<image>'."\r\n";
		echo "\t\t".'<url>http://static.swisslinux.org/images/logo.png</url>'."\r\n";
		echo "\t\t".'<title>Swisslinux.org\'s Logo</title>'."\r\n";
		echo "\t\t".'<link>'.$pun_config['o_base_url'].'/</link>'."\r\n";
		echo "\t".'</image>'."\r\n";
 
		// get the 15 newest post, and other usefull stuff
		$result = $db->query('
SELECT t.id, p.poster, t.subject, t.posted, t.last_post, f.id AS fid, f.forum_name, p.id AS pid, p.message, fi.icon
FROM
'.$db->prefix.'posts AS p
LEFT JOIN '.$db->prefix.'topics AS t ON t.id=p.topic_id
INNER JOIN '.$db->prefix.'forums AS f ON f.id=t.forum_id
LEFT JOIN '.$db->prefix.'forum_perms AS fp ON (fp.forum_id=f.id AND fp.group_id=3)
LEFT JOIN '.$db->prefix.'forum_icon AS fi ON fi.forum_id=f.id
WHERE (fp.read_forum IS NULL OR fp.read_forum=1) AND t.moved_to IS NULL'.$forum_sql.' ORDER BY p.posted DESC LIMIT 15
') or error('Unable to fetch post list', __FILE__, __LINE__, $db->error());
 
		// we want to be able to parse the message
		include('include/parser.php');
 
		// let's write the items
		while ($cur_topic = $db->fetch_assoc($result))
		{
			if ($pun_config['o_censoring'] == '1') {
				$cur_topic['subject'] = censor_words($cur_topic['subject']);
				$cur_topic['message'] = censor_words($cur_topic['message']);
				}
 
			echo "\t".'<item>'."\r\n";
			echo "\t\t".'<title>'.pun_htmlspecialchars($cur_topic['subject']).'</title>'."\r\n";
			echo "\t\t".'<link>'.$pun_config['o_base_url'].'/viewtopic.php?pid='.$cur_topic['pid'].'#p'.$cur_topic['pid'].'</link>'."\r\n";
			echo "\t\t".'<description><![CDATA['.escape_cdata($lang_common['Forum']).':'."\r\n";
 			echo "\t\t\t".escape_cdata('<img src="'.$pun_config['o_base_url'].'/img/icons/'.$cur_topic['icon'].'" alt="'.$cur_topic['icon'].'" />'."\r\n");
			echo "\t\t\t".escape_cdata('<a href="'.$pun_config['o_base_url'].'/viewforum.php?id='.$cur_topic['fid'].'">'.$cur_topic['forum_name'].'</a><br />'."\r\n".$lang_common['Author'].': '.$cur_topic['poster'].'<br />'."\r\n".$lang_common['Posted'].': '.date('r', $cur_topic['last_post'])."\r\n");
 			echo "\t\t\t".'<br />'."\r\n";
			echo escape_cdata(parse_message($cur_topic['message'],FALSE));
			echo ']]>'."\r\n"."\t\t".'</description>'."\r\n";
			echo "\t\t".escape_cdata('<guid>'.$pun_config['o_base_url'].'/viewtopic.php?pid='.$cur_topic['pid'].'#p'.$cur_topic['pid'].'</guid>'."\r\n");
			echo "\t".'</item>'."\r\n";
		}
 
		echo '</channel>'."\r\n";
		echo '</rss>';
	}
 
// ***** END rewritten by fbianco for Swisslinux.org *****//

Do not forget to edit the part of the script after :

// *** Added for Swisslinux.org ***** //

else you will get the Swisslinux.org's logo on your rss feed.