### FeedWriter.php

<?php

require_once 'FeedWriterItem.php';
require_once 'FeedWriterTitle.php';

abstract class FeedWriter {
    /**
     * Write feed. Needs subclass to work.
     *
     * @param Array of FeedWriter Item instances
     * @param FeedWriterTitle instance
     */
    public function main(&$arrItems, &$title) {
        // Send headers
        if (headers_sent() === false) {
            header("Last-Modified: " . date("D, M j Y G:i:s O", $title->lastUpdated));
            $this->sendHeader();
        }
  
        $this->printTitle($title);
  
        foreach($arrItems as $item) {
            $this->printItem($item);
        }
  
        $this->printEnd();
    }
  
    protected function sendHeader() {
        header("Content-Type: text/xml");
    }
  
    abstract protected function printItem($item);
  
    abstract protected function printTitle($title);
  
    abstract protected function printEnd();
}


### FeedWriterItem.php 
<?php
  /**
* Simple Date Structure holding feed item data
*/
class FeedWriterItem {
  public $description = '';
  public $title = '';
  public $link = '';
  public $pubDate = ''; // this is a date, no string!
  public $guid = '';
  public $author = '';
  public $content = '';
}

### FeedWriterRssWriter.php 
<?php
require_once 'FeedWriter.php';

class FeedWriterRssWriter extends FeedWriter {  
    protected function sendHeader() {
        header("Content-Type: text/xml");
    }
  
    protected function printItem($item) {
        ?>
  <item>
    <title><?php print $item->title; ?></title>
    <link><?php print $item->link; ?></link>
    <description><?php print $item->description; ?></description>
    <content:encoded><?php print $item->content; ?></content:encoded>
    <pubDate><?php print date(DATE_RFC822, $item->pubDate); ?></pubDate>
    <guid isPermaLink="true"><?php print $item->guid; ?></guid>
    <author><?php print $item->author; ?></author>
  </item>
  <?php
    }
  
    protected function printTitle($title) {
        print '<?xml version="1.0" encoding="' . $title->encoding . '"?>';
  ?>
  <rss version="2.0"
    xmlns:content="http://purl.org/rss/1.0/modules/content/"
    xmlns:wfw="http://wellformedweb.org/CommentAPI/"
  >
  <channel>
    <title><?php print $title->title; ?></title>
    <link><?php print $title->link; ?></link>
    <description><?php print $title->description; ?></description>
    <language>de</language>
    <pubDate><?php print date(DATE_RFC822, $title->lastUpdated); ?></pubDate>
    <generator><?php print $title->generator; ?></generator>
    <image>
      <title><?php print $title->title; ?></title>
      <link><?php print $title->link; ?></link>
      <url><?php print $title->imageURL; ?></url>
    </image>
  <?php
    }
  
    protected function printEnd() {
  ?>
  </channel>
  </rss>
  <?php
    }
}

### FeedWriterTitle.php 
<?php

  /**
 * Simple Date Structure holding feed data
 */
class FeedWriterTitle {
    public $title = '';
    public $lastUpdated = ''; // this is a date, no string!
    public $description = '';
    public $link = '';
    public $imageURL = '';
    public $generator = '';
    public $encoding = 'Utf-8';
}