rssfeed.php

<?php
function getItems() {
    $items = array();
    // Get items from somewhere
    return $items;
}

echo "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n";
?>
<rss version="2.0">
  <channel>
    <title>Simple RSS 2.0 Feed</title>
    <link>http://www.example.com</link>
    <description>Simple RSS 2.0 Feed</description>
    <?php foreach(getItems() as $item): ?>
      <item>
        <title><?php echo $item['title']; ?></title>
        <link><?php echo $item['url']; ?></link>
        <description><?php echo $item['description']; ?></description>
        <pubDate><?php echo date('r', $item['date']); ?></pubDate>
      </item>
    <?php endforeach; ?>
  </channel>
</rss>