以下为引用的内容：

/**
 * An FeedHtmlField describes and generates
 * a feed, item or image html field (probably a description). Output is
 * generated based on $truncSize, $syndicateHtml properties.
 * author Pascal Van Hecke <feedcreator.class.phpvanhecke.info>
 * version 1.6
 */
class FeedHtmlField {
 /**
  * Mandatory attributes of a FeedHtmlField.
  */
 var $rawFieldContent;
 
 /**
  * Optional attributes of a FeedHtmlField.
  *
  */
 var $truncSize, $syndicateHtml;
 
 /**
  * Creates a new instance of FeedHtmlField.
  * param  $string: if given, sets the rawFieldContent property
  */
 function FeedHtmlField($parFieldContent) {
  if ($parFieldContent) {
   $this->rawFieldContent = $parFieldContent;
  }
 }
  
  /**
  * Creates the right output, depending on $truncSize, $syndicateHtml properties.
  * return string    the formatted field
  */
 function output() {
  // when field available and syndicated in html we assume
  // - valid html in $rawFieldContent and we enclose in CDATA tags
  // - no truncation (truncating risks producing invalid html)
  if (!$this->rawFieldContent) {
   $result = "";
  } elseif ($this->syndicateHtml) {
   $result = "<![CDATA[".$this->rawFieldContent."]]>";
  } else {
   if ($this->truncSize and is_int($this->truncSize)) {
    $result = FeedCreator::iTrunc(htmlspecialchars($this->rawFieldContent),$this->truncSize);
   } else {
    $result = htmlspecialchars($this->rawFieldContent);
   }
  }
  return $result;
 }
}

/**
 * UniversalFeedCreator lets you choose during runtime which
 * format to build.
 * For general usage of a feed class, see the FeedCreator class
 * below or the example above.
 *
 * since 1.3
 * author Kai Blankenhorn <kaibbitfolge.de>
 */
class UniversalFeedCreator extends FeedCreator {
 var $_feed;
 
 function _setFormat($format) {
  switch (strtoupper($format)) {
  
   case "2.0":
    // fall through
   case "RSS2.0":
    $this->_feed = new RSSCreator20();
    break;
  
   case "0.91":
    // fall through
   case "RSS0.91":
    $this->_feed = new RSSCreator091();
    break;
  
   default:
    $this->_feed = new RSSCreator091();
    break;
  }
       
  $vars = get_object_vars($this);
  foreach ($vars as $key => $value) {
   // prevent overwriting of properties "contentType", "encoding"; do not copy "_feed" itself
   if (!in_array($key, array("_feed", "contentType", "encoding"))) {
    $this->_feed->{$key} = $this->{$key};
   }
  }
 }
 
 /**
  * Creates a syndication feed based on the items previously added.
  *
  * see        FeedCreator::addItem()
  * param    string    format    format the feed should comply to. Valid values are:
  *   "PIE0.1", "mbox", "RSS0.91", "RSS1.0", "RSS2.0", "OPML", "ATOM0.3", "HTML", "JS"
  * return    string    the contents of the feed.
  */
 function createFeed($format = "RSS0.91") {
  $this->_setFormat($format);
  return $this->_feed->createFeed();
 }
 
 
  /**
  * Saves this feed as a file on the local disk. After the file is saved, an HTTP redirect
  * header may be sent to redirect the use to the newly created file.
  * since 1.4
  *
  * param string format format the feed should comply to. Valid values are:
  *   "PIE0.1" (deprecated), "mbox", "RSS0.91", "RSS1.0", "RSS2.0", "OPML", "ATOM", "ATOM0.3", "HTML", "JS"
  * param string filename optional the filename where a recent version of the feed is saved. If not specified, the filename is $_SERVER["PHP_SELF"] with the extension changed to .xml (see _generateFilename()).
  * param boolean displayContents optional send the content of the file or not. If true, the file will be sent in the body of the response.
  */
 function saveFeed($format="RSS0.91", $filename="", $displayContents=true) {
  $this->_setFormat($format);
  $this->_feed->saveFeed($filename, $displayContents);
 }

   /**
    * Turns on caching and checks if there is a recent version of this feed in the cache.
    * If there is, an HTTP redirect header is sent.
    * To effectively use caching, you should create the FeedCreator object and call this method
    * before anything else, especially before you do the time consuming task to build the feed
    * (web fetching, for example).
    *
    * param   string   format   format the feed should comply to. Valid values are:
    *       "PIE0.1" (deprecated), "mbox", "RSS0.91", "RSS1.0", "RSS2.0", "OPML", "ATOM0.3".
    * param filename   string   optional the filename where a recent version of the feed is saved. If not specified, the filename is $_SERVER["PHP_SELF"] with the extension changed to .xml (see _generateFilename()).
    * param timeout int      optional the timeout in seconds before a cached version is refreshed (defaults to 3600 = 1 hour)
    */
   function useCached($format="RSS0.91", $filename="", $timeout=3600) {
      $this->_setFormat($format);
      $this->_feed->useCached($filename, $timeout);
   }
}

/**
 * FeedCreator is the abstract base implementation for concrete
 * implementations that implement a specific format of syndication.
 *
 * abstract
 * author Kai Blankenhorn <kaibbitfolge.de>
 * since 1.4
 */
class FeedCreator extends HtmlDescribable {
 /**
  * Mandatory attributes of a feed.
  */
 var $title, $description, $link;
 
 
 /**
  * Optional attributes of a feed.
  */
 var $syndicationURL, $image, $language, $copyright, $pubDate, $lastBuildDate, $editor, $editorEmail, $webmaster, $category, $docs, $ttl, $rating, $skipHours, $skipDays;
 /**
 * The url of the external xsl stylesheet used to format the naked rss feed.
 * Ignored in the output when empty.
 */
 var $xslStyleSheet = "";
 
 
 /**
  * access private
  */
 var $items = Array();
 
 
 /**
  * This feed's MIME content type.
  * since 1.4
  * access private
  */
 var $contentType = "application/xml";
 
 
 /**
  * This feed's character encoding.
  * since 1.6.1
  **/
 var $encoding = "utf-8";
 
 
 /**
  * Any additional elements to include as an assiciated array. All $key => $value pairs
  * will be included unencoded in the feed in the form
  *     <$key>$value</$key>
  * Again: No encoding will be used! This means you can invalidate or enhance the feed
  * if $value contains markup. This may be abused to embed tags not implemented by
  * the FeedCreator class used.
  */
 var $additionalElements = Array();
  
   
 /**
  * Adds an FeedItem to the feed.
  *
  * param object FeedItem $item The FeedItem to add to the feed.
  * access public
  */
 function addItem($item) {
  $this->items[] = $item;
 }
 /**
  * 清空当前数组值
  *
  * param object FeedItem $item The FeedItem to add to the feed.
  * access public
  */
  function clearItem2Null() {
  $this->items = array();
 }
 
 /**
  * Truncates a string to a certain length at the most sensible point.
  * First, if there's a '.' character near the end of the string, the string is truncated after this character.
  * If there is no '.', the string is truncated after the last ' ' character.
  * If the string is truncated, " ..." is appended.
  * If the string is already shorter than $length, it is returned unchanged.
  *
  * static
  * param string    string A string to be truncated.
  * param int        length the maximum length the string should be truncated to
  * return string    the truncated string
  */
 function iTrunc($string, $length) {
  if (strlen($string)<=$length) {
   return $string;
  }
 
  $pos = strrpos($string,".");
  if ($pos>=$length-4) {
   $string = substr($string,0,$length-4);
   $pos = strrpos($string,".");
  }
  if ($pos>=$length*0.4) {
   return substr($string,0,$pos+1)." ...";
  }
 
  $pos = strrpos($string," ");
  if ($pos>=$length-4) {
   $string = substr($string,0,$length-4);
   $pos = strrpos($string," ");
  }
  if ($pos>=$length*0.4) {
   return substr($string,0,$pos)." ...";
  }
 
  return substr($string,0,$length-4)." ...";
  
 }
 
 
 /**
  * Creates a comment indicating the generator of this feed.
  * The format of this comment seems to be recognized by
  * Syndic8.com.
  */
 function _createGeneratorComment() {
  return "<!-- generator=\"".FEEDCREATOR_VERSION."\" -->\n";
 }
 
 
 /**
  * Creates a string containing all additional elements specified in
  * $additionalElements.
  * param elements array an associative array containing key => value pairs
  * param indentString string a string that will be inserted before every generated line
  * return    string    the XML tags corresponding to $additionalElements
  */
 function _createAdditionalElements($elements, $indentString="") {
  $ae = "";
  if (is_array($elements)) {
   foreach($elements AS $key => $value) {
    $ae.= $indentString."<$key>$value</$key>\n";
   }
  }
  return $ae;
 }
 
 function _createStylesheetReferences() {
  $xml = "";
  if ($this->cssStyleSheet) $xml .= "<?xml-stylesheet href=\"".$this->cssStyleSheet."\" _fcksavedurl="\"".$this->cssStyleSheet."\"" type=\"text/css\"?>\n";
  if ($this->xslStyleSheet) $xml .= "<?xml-stylesheet href=\"".$this->xslStyleSheet."\" type=\"text/xsl\"?>\n";
  return $xml;
 }
 
 
 /**
  * Builds the feed's text.
  * abstract
  * return    string    the feed's complete text
  */
 function createFeed() {
 }
 
 /**
  * Generate a filename for the feed cache file. The result will be $_SERVER["PHP_SELF"] with the extension changed to .xml.
  * For example:
  *
  * echo $_SERVER["PHP_SELF"]."\n";
  * echo FeedCreator::_generateFilename();
  *
  * would produce:
  *
  * /rss/latestnews.php
  * latestnews.xml
  *
  * return string the feed cache filename
  * since 1.4
  * access private
  */
 function _generateFilename() {
  $fileInfo = pathinfo($_SERVER["PHP_SELF"]);
  return substr($fileInfo["basename"],0,-(strlen($fileInfo["extension"])+1)).".xml";
 }