A PHP function for simultaneously building 'flat' (hardcoded) RSS, Atom, and Sitemap XMLs...

script_builder.php

<?php

// Called after an insertion or update to the `posts` table
// Returns void
function writeScripts() {
	$atom_date = getDateRFC(getD()); // Current Date 3339 for Atom feed
	$site_date = getDateSite(getD()); // Current Date YYYY-MM-DD for Sitemap

	// Beginning of Atom.xml
	$atom_str = '<feed xml:lang="en-US" xmlns="http://www.w3.org/2005/Atom"> 
	<title>L2Program</title> 
	<subtitle>L2Program.co.uk Atom Feed</subtitle>
	<link href="http://www.l2program.co.uk/atom.xml" rel="self"/> 
	<updated>'.$atom_date.'</updated>
	<author> 
		<name>Joss Whittle</name>
		<email>admin@l2program.co.uk</email>
	</author>
	<id>tag:L2Program.co.uk,2012:http://www.l2program.co.uk/atom.xml</id>';

	// Beginning of Rss.xml
	$rss_str = '<?xml version="1.0" encoding="ISO-8859-1"?>
<rss version="2.0">
	<channel>
		<title>L2Program</title>
		<link>http://www.l2program.co.uk/rss.xml</link>
		<description>L2Program.co.uk RSS Feed</description>
		<language>en-us</language>
		<copyright></copyright>';

	// Beginning of Sitemap.xml
	$site_str = '<?xml version="1.0" encoding="UTF-8"?>  
<urlset xmlns="http://www.google.com/schemas/sitemap/0.84">
	<url>  
		<loc>http://www.l2program.co.uk/</loc>  
		<lastmod>'.$site_date.'</lastmod>  
		<changefreq>daily</changefreq>  
		<priority>1.0</priority>  
	</url>';

	// Get all the posts in reverse chronological order and loop through them
	$q = mysql_query("SELECT * FROM `posts` ORDER BY `id` DESC");
	while ($r = mysql_fetch_array($q)) {

		// This is my format function, it runs a series of REGEX's on the plain text 
		// body of an article to swap my short hands for HTML tags
		$body = fArticle($r['body']);

		// To embed this in RSS or Atom we have to strip everything except p, a, 
		// img, ul, and li tags, and fix the links from being local to absolute
		$content = strip_tags($body, '<p><a><img><ul><li>');
		$content = preg_replace("/\"\/ext/i", '"http://www.l2program.co.uk/ext', $content);

		// The URL for this article
		$url = 'http://www.l2program.co.uk/post/'.$r['id'].'/'.parseTitle($r['title']);

		// Add a node to the Atom Feed for this post
		$atom_str .= '	<entry>
		<title>'.$r['title'].'</title>
		<link type="text/html" href="'.$url.'"/>
		<id>tag:L2Program.co.uk,2012:'.$url.'</id>
		<updated>'.getDateRFC($r['lastmod']).'</updated>
		<author>
			<name>Joss Whittle</name>
		</author>
		<content type="html">'.htmlspecialchars($content).'</content>
	</entry>
';

		// Add a node to the RSS Feed for this post
		$rss_str .= '		<item>
			<title>'.$r['title'].'</title>
			<description>'.htmlspecialchars($content).'</description>
			<link>'.$url.'</link>
			<pubDate>'.getDateRSS($r['lastmod']).'</pubDate>
		</item>
';

		// Add a node to the Sitemap for this post
		$site_str .= '	<url>  
		<loc>'.$url.'</loc>  
		<lastmod>'.getDateSite($r['lastmod']).'</lastmod>  
		<changefreq>daily</changefreq>  
		<priority>0.9</priority>  
	</url>
';
	}

	// Clean up and close all the feeds
	$atom_str .= '</feed>';

	$rss_str .= '	</channel>
</rss>';

	$site_str .= '</urlset>';

	// Write the three feeds to their corresponding files in the root of the website
	$fp = fopen('../../atom.xml', 'w');
	fwrite($fp, $atom_str);
	fclose($fp);

	$fp = fopen('../../rss.xml', 'w');
	fwrite($fp, $rss_str);
	fclose($fp);

	$fp = fopen('../../sitemap.xml', 'w');
	fwrite($fp, $site_str);
	fclose($fp);
}
?>