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 <[email protected]>
 * @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 <[email protected]>
 */
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 <[email protected]>
 * @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";
 }

以下为引用的内容：

 /**
 * FeedDate is an internal class that stores a date for a feed or feed item.
 * Usually, you won't need to use this.
 */
class FeedDate {
 var $unix;
 
 /**
  * Creates a new instance of FeedDate representing a given date.
  * Accepts RFC 822, ISO 8601 date formats as well as unix time stamps.
  * @param mixed $dateString optional the date this FeedDate will represent. If not specified, the current date and time is used.
  */
 function FeedDate($dateString="") {
  if ($dateString=="") $dateString = date("r");
 
  if (is_integer($dateString)) {
   $this->unix = $dateString;
   return;
  }
  if (preg_match("~(?:(?:Mon|Tue|Wed|Thu|Fri|Sat|Sun),\\s+)?(\\d{1,2})\\s+([a-zA-Z]{3})\\s+(\\d{4})\\s+(\\d{2}):(\\d{2}):(\\d{2})\\s+(.*)~",$dateString,$matches)) {
   $months = Array("Jan"=>1,"Feb"=>2,"Mar"=>3,"Apr"=>4,"May"=>5,"Jun"=>6,"Jul"=>7,"Aug"=>8,"Sep"=>9,"Oct"=>10,"Nov"=>11,"Dec"=>12);
   $this->unix = mktime($matches[4],$matches[5],$matches[6],$months[$matches[2]],$matches[1],$matches[3]);
   if (substr($matches[7],0,1)=='+' or substr($matches[7],0,1)=='-') {
    $tzOffset = (substr($matches[7],0,3) * 60 + substr($matches[7],-2)) * 60;
   } else {
    if (strlen($matches[7])==1) {
     $oneHour = 3600;
     $ord = ord($matches[7]);
     if ($ord < ord("M")) {
      $tzOffset = (ord("A") - $ord - 1) * $oneHour;
     } elseif ($ord >= ord("M") AND $matches[7]!="Z") {
      $tzOffset = ($ord - ord("M")) * $oneHour;
     } elseif ($matches[7]=="Z") {
      $tzOffset = 0;
     }
    }
    switch ($matches[7]) {
     case "UT":
     case "GMT": $tzOffset = 0;
    }
   }
   $this->unix += $tzOffset;
   return;
  }
  if (preg_match("~(\\d{4})-(\\d{2})-(\\d{2})T(\\d{2}):(\\d{2}):(\\d{2})(.*)~",$dateString,$matches)) {
   $this->unix = mktime($matches[4],$matches[5],$matches[6],$matches[2],$matches[3],$matches[1]);
   if (substr($matches[7],0,1)=='+' or substr($matches[7],0,1)=='-') {
    $tzOffset = (substr($matches[7],0,3) * 60 + substr($matches[7],-2)) * 60;
   } else {
    if ($matches[7]=="Z") {
     $tzOffset = 0;
    }
   }
   $this->unix += $tzOffset;
   return;
  }
  $this->unix = 0;
 }
 /**
  * Gets the date stored in this FeedDate as an RFC 822 date.
  *
  * @return a date in RFC 822 format
  */
 function rfc822() {
  //return gmdate("r",$this->unix);
  $date = gmdate("Y-m-d H:i:s", $this->unix);
  if (TIME_ZONE!="") $date .= " ".str_replace(":","",TIME_ZONE);
  return $date;
 }
 
 /**
  * Gets the date stored in this FeedDate as an ISO 8601 date.
  *
  * @return a date in ISO 8601 format
  */
 function iso8601() {
  $date = gmdate("Y-m-d H:i:s",$this->unix);
  $date = substr($date,0,22) . ':' . substr($date,-2);
  if (TIME_ZONE!="") $date = str_replace("+00:00",TIME_ZONE,$date);
  return $date;
 }
 
 /**
  * Gets the date stored in this FeedDate as unix time stamp.
  *
  * @return a date as a unix time stamp
  */
 function unix() {
  return $this->unix;
 }
}

/**
 * RSSCreator10 is a FeedCreator that implements RDF Site Summary (RSS) 1.0.
 *
 * @see http://www.purl.org/rss/1.0/
 * @since 1.3
 * @author Kai Blankenhorn <[email protected]>
 */
class RSSCreator10 extends FeedCreator {
 /**
  * Builds the RSS feed's text. The feed will be compliant to RDF Site Summary (RSS) 1.0.
  * The feed will contain all items previously added in the same order.
  * @return    string    the feed's complete text
  */
 function createFeed() {    
  $feed = "<?xml version=\"1.0\" encoding=\"".$this->encoding."\"?>\n";
  $feed.= $this->_createGeneratorComment();
  if ($this->cssStyleSheet=="") {
   $cssStyleSheet = "http://www.w3.org/2000/08/w3c-synd/style.css";
  }
  $feed.= $this->_createStylesheetReferences();
  $feed.= "<rdf:RDF\n";
  $feed.= "    xmlns=\"http://purl.org/rss/1.0/\"\n";
  $feed.= "    xmlns:rdf=\"http://www.w3.org/1999/02/22-rdf-syntax-ns#\"\n";
  $feed.= "    xmlns:slash=\"http://purl.org/rss/1.0/modules/slash/\"\n";
  $feed.= "    xmlns:dc=\"http://purl.org/dc/elements/1.1/\">\n";
  $feed.= "    <channel rdf:about=\"".$this->syndicationURL."\">\n";
  $feed.= "        <title>".htmlspecialchars($this->title)."</title>\n";
  $feed.= "        <description>".htmlspecialchars($this->description)."</description>\n";
  $feed.= "        <link>".$this->link."</link>\n";
  if ($this->image!=null) {
   $feed.= "        <image rdf:resource=\"".$this->image->url."\" />\n";
  }
  $now = new FeedDate();
  $feed.= "       <dc:date>".htmlspecialchars($now->iso8601())."</dc:date>\n";
  $feed.= "        <items>\n";
  $feed.= "            <rdf:Seq>\n";
  for ($i=0;$i<count($this->items);$i++) {
   $feed.= "                <rdf:li rdf:resource=\"".htmlspecialchars($this->items[$i]->link)."\"/>\n";
  }
  $feed.= "            </rdf:Seq>\n";
  $feed.= "        </items>\n";
  $feed.= "    </channel>\n";
  if ($this->image!=null) {
   $feed.= "    <image rdf:about=\"".$this->image->url."\">\n";
   $feed.= "        <title>".$this->image->title."</title>\n";
   $feed.= "        <link>".$this->image->link."</link>\n";
   $feed.= "        <url>".$this->image->url."</url>\n";
   $feed.= "    </image>\n";
  }
  $feed.= $this->_createAdditionalElements($this->additionalElements, "    ");
 
  for ($i=0;$i<count($this->items);$i++) {
   $feed.= "    <item rdf:about=\"".htmlspecialchars($this->items[$i]->link)."\">\n";
   //$feed.= "        <dc:type>Posting</dc:type>\n";
   $feed.= "        <dc:format>text/html</dc:format>\n";
   if ($this->items[$i]->date!=null) {
    $itemDate = new FeedDate($this->items[$i]->date);
    $feed.= "        <dc:date>".htmlspecialchars($itemDate->iso8601())."</dc:date>\n";
   }
   if ($this->items[$i]->source!="") {
    $feed.= "        <dc:source>".htmlspecialchars($this->items[$i]->source)."</dc:source>\n";
   }
   if ($this->items[$i]->author!="") {
    $feed.= "        <dc:creator>".htmlspecialchars($this->items[$i]->author)."</dc:creator>\n";
   }
   $feed.= "        <title>".htmlspecialchars(strip_tags(strtr($this->items[$i]->title,"\n\r","  ")))."</title>\n";
   $feed.= "        <link>".htmlspecialchars($this->items[$i]->link)."</link>\n";
   $feed.= "        <description>".htmlspecialchars($this->items[$i]->description)."</description>\n";
   $feed.= $this->_createAdditionalElements($this->items[$i]->additionalElements, "        ");
   $feed.= "    </item>\n";
  }
  $feed.= "</rdf:RDF>\n";
  return $feed;
 }
}
 
/**
 * RSSCreator091 is a FeedCreator that implements RSS 0.91 Spec, revision 3.
 *
 * @see http://my.netscape.com/publish/formats/rss-spec-0.91.html
 * @since 1.3
 * @author Kai Blankenhorn <[email protected]>
 */
class RSSCreator091 extends FeedCreator {
 /**
  * Stores this RSS feed's version number.
  * @access private
  */
 var $RSSVersion;
 function RSSCreator091() {
  $this->_setRSSVersion("0.91");
  $this->contentType = "application/rss+xml";
 }
 
 /**
  * Sets this RSS feed's version number.
  * @access private
  */
 function _setRSSVersion($version) {
  $this->RSSVersion = $version;
 }
 /**
  * Builds the RSS feed's text. The feed will be compliant to RDF Site Summary (RSS) 1.0.
  * The feed will contain all items previously added in the same order.
  * @return    string    the feed's complete text
  */
 function createFeed() {
  $feed = "<?xml version=\"1.0\" encoding=\"".$this->encoding."\"?>\n";
  $feed.= $this->_createGeneratorComment();
  $feed.= $this->_createStylesheetReferences();
  $feed.= "<rss version=\"".$this->RSSVersion."\">\n";
  $feed.= "    <channel>\n";
  $feed.= "        <title>".FeedCreator::iTrunc(htmlspecialchars($this->title),100)."</title>\n";
  $this->descriptionTruncSize = 500;
  $feed.= "        <description>".$this->getDescription()."</description>\n";
  $feed.= "        <link>".$this->link."</link>\n";
  $now = new FeedDate();
  $feed.= "        <lastBuildDate>".htmlspecialchars($now->rfc822())."</lastBuildDate>\n";
  $feed.= "        <generator>".FEEDCREATOR_VERSION."</generator>\n";
  if ($this->image!=null) {
   $feed.= "        <image>\n";
   $feed.= "            <url>".$this->image->url."</url>\n";
   $feed.= "            <title>".FeedCreator::iTrunc(htmlspecialchars($this->image->title),100)."</title>\n";
   $feed.= "            <link>".$this->image->link."</link>\n";
   if ($this->image->width!="") {
    $feed.= "            <width>".$this->image->width."</width>\n";
   }
   if ($this->image->height!="") {
    $feed.= "            <height>".$this->image->height."</height>\n";
   }
   if ($this->image->description!="") {
    $feed.= "            <description>".$this->image->getDescription()."</description>\n";
   }
   $feed.= "        </image>\n";
  }
  if ($this->language!="") {
   $feed.= "        <language>".$this->language."</language>\n";
  }
  if ($this->copyright!="") {
   $feed.= "        <copyright>".FeedCreator::iTrunc(htmlspecialchars($this->copyright),100)."</copyright>\n";
  }
  if ($this->editor!="") {
   $feed.= "        <managingEditor>".FeedCreator::iTrunc(htmlspecialchars($this->editor),100)."</managingEditor>\n";
  }
  if ($this->webmaster!="") {
   $feed.= "        <webMaster>".FeedCreator::iTrunc(htmlspecialchars($this->webmaster),100)."</webMaster>\n";
  }
  if ($this->pubDate!="") {
   $pubDate = new FeedDate($this->pubDate);
   $feed.= "        <pubDate>".htmlspecialchars($pubDate->rfc822())."</pubDate>\n";
  }
  if ($this->category!="") {
   $feed.= "        <category>".htmlspecialchars($this->category)."</category>\n";
  }
  if ($this->docs!="") {
   $feed.= "        <docs>".FeedCreator::iTrunc(htmlspecialchars($this->docs),500)."</docs>\n";
  }
  if ($this->ttl!="") {
   $feed.= "        <ttl>".htmlspecialchars($this->ttl)."</ttl>\n";
  }
  if ($this->rating!="") {
   $feed.= "        <rating>".FeedCreator::iTrunc(htmlspecialchars($this->rating),500)."</rating>\n";
  }
  if ($this->skipHours!="") {
   $feed.= "        <skipHours>".htmlspecialchars($this->skipHours)."</skipHours>\n";
  }
  if ($this->skipDays!="") {
   $feed.= "        <skipDays>".htmlspecialchars($this->skipDays)."</skipDays>\n";
  }
  $feed.= $this->_createAdditionalElements($this->additionalElements, "    ");
  for ($i=0;$i<count($this->items);$i++) {
   $feed.= "        <item>\n";
   $feed.= "            <title>".FeedCreator::iTrunc(htmlspecialchars(strip_tags($this->items[$i]->title)),100)."</title>\n";
   $feed.= "            <link>".htmlspecialchars($this->items[$i]->link)."</link>\n";
   $feed.= "            <description>".$this->items[$i]->getDescription()."</description>\n";
  
   if ($this->items[$i]->author!="") {
    $feed.= "            <author>".htmlspecialchars($this->items[$i]->author)."</author>\n";
   }
   /*
   // on hold
   if ($this->items[$i]->source!="") {
     $feed.= "            <source>".htmlspecialchars($this->items[$i]->source)."</source>\n";
   }
   */
   if ($this->items[$i]->category!="") {
    $feed.= "            <category>".htmlspecialchars($this->items[$i]->category)."</category>\n";
   }
   if ($this->items[$i]->comments!="") {
    $feed.= "            <comments>".htmlspecialchars($this->items[$i]->comments)."</comments>\n";
   }
   if ($this->items[$i]->date!="") {
   $itemDate = new FeedDate($this->items[$i]->date);
    $feed.= "            <pubDate>".htmlspecialchars($itemDate->rfc822())."</pubDate>\n";
   }
   if ($this->items[$i]->guid!="") {
    $feed.= "            <guid>".htmlspecialchars($this->items[$i]->guid)."</guid>\n";
   }
   $feed.= $this->_createAdditionalElements($this->items[$i]->additionalElements, "        ");
   $feed.= "        </item>\n";
  }
  $feed.= "    </channel>\n";
  $feed.= "</rss>\n";
  return $feed;
 }
}
 
/**
 * RSSCreator20 is a FeedCreator that implements RDF Site Summary (RSS) 2.0.
 *
 * @see http://backend.userland.com/rss
 * @since 1.3
 * @author Kai Blankenhorn <[email protected]> */
class RSSCreator20 extends RSSCreator091 {
    function RSSCreator20() {
        parent::_setRSSVersion("2.0");
    }
   
}