php生成RSS订阅的方法

本文实例讲述了PHP 生成 RSS 订阅的方法。分享给大家供大家参考。具体分析如下：

RSS（简易信息聚合，也叫聚合内容）是一种描述和同步网站内容的格式。RSS可以是以下三个解释的其中一个： Really Simple Syndication；RDF (Resource Description Framework) Site Summary； Rich Site Summary。但其实这三个解释都是指同一种Syndication的技术。RSS目前广泛用于网上新闻频道，blog和wiki。使用RSS 订阅能更快地获取信息，网站提供RSS 输出，有利于让用户获取网站内容的最新更新。网络用户可以在客户端借助于支持 RSS的聚合工具软件，在不打开网站内容页面的情况下阅读支持 RSS 输出的网站内容。从技术上来说一个RSS 文件就是一段规范的XML数据，该文件一般以RSS，xml或者rdf作为后缀，下面是一段 RSS 文件的内容示例：

代码如下:

<RSS version="2.0"> 编程之家 //www.jb51.cc/ 编程之家 <a href="/tag/RSS/" target="_blank" class="keywords">RSS</a> Tutorial 网站地址/RSS New RSS tutorial on W3School XML Tutorial 网站地址/xml New XML tutorial on W3School

下面分享一段使用 PHP 动态生成 RSS 的代码示例：

代码如下:

class FeedImage extends HtmlDescribable{
var $title,$url,$link;
var $width,$height,$description;
}

class HtmlDescribable{
var $descriptionHtmlSyndicated;
var $descriptionTruncSize;

function getDescription(){
$descriptionField=new FeedHtmlField($this->description);
$descriptionField->syndicateHtml=$this->descriptionHtmlSyndicated;
$descriptionField->truncSize=$this->descriptionTruncSize;
return $descriptionField->output();
}
}

class FeedHtmlField{
var $rawFieldContent;
var $truncSize,$syndicateHtml;
function FeedHtmlField($parFieldContent){
if($parFieldContent){
$this->rawFieldContent=$parFieldContent;
}
}
function output(){
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;
}
}

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;
}
$vars=get_objectvars($this);
foreach ($vars as $key => $value){
// prevent overwriting of properties "contentType","encoding"; do not copy "Feed" itself
if(!inarray($key,array("Feed","contentType","encoding"))){
$this->_Feed->{$key}=$this->{$key};
}
}
}

function createFeed($format="RSS0.91"){
$this->setFormat($format);
return $this->Feed->createFeed();
}

function saveFeed($format="RSS0.91",$filename="",$displayContents=true){
$this->setFormat($format);
$this->Feed->saveFeed($filename,$displayContents);
}

function useCached($format="RSS0.91",$timeout=3600){
$this->setFormat($format);
$this->Feed->useCached($filename,$timeout);
}
}

class FeedCreator extends HtmlDescribable{
var $title,$link;
var $syndicationURL,$language,$copyright,$pubDate,$lastBuildDate,$editor,$editorEmail,$webmaster,$docs,$ttl,$rating,$skipHours,$skipDays;
var $xslStyleSheet="";
var $items=Array();
var $contentType="application/xml";
var $encoding="utf-8";
var $additionalElements=Array();

function addItem($item){
$this->items[]=$item;
}

function clearItem2Null(){
$this->items=array();
}

function iTrunc($string,$length){
if(strlen($string)<=$length){
return $string;
}

$pos=strrpos($string,".");
if($pos>=$length-4){
$string=substr($string,$length-4);
$pos=strrpos($string,".");
}
if($pos>=$length*0.4){
return substr($string,$pos+1)." ...";
}

$pos=strrpos($string," ");
if($pos>=$length-4){
$string=substr($string," ");
}
if($pos>=$length*0.4){
return substr($string,$pos)." ...";
}

return substr($string,$length-4)." ...";
}

function _createGeneratorComment(){
return "\n";
}

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."\" type=\"text/css\"?>\n";
if($this->xslStyleSheet) $xml .= "<?xml-stylesheet href=\"".$this->xslStyleSheet."\" type=\"text/xsl\"?>\n";
return $xml;
}

function createFeed(){}

function _generateFilename(){
$fileInfo=pathinfo($_SERVER["PHP_SELF"]);
return substr($fileInfo["basename"],-(strlen($fileInfo["extension"])+1)).".xml";
}

function _redirect($filename){
Header("Content-Type: ".$this->contentType."; charset=".$this->encoding."; filename=".basename($filename));
Header("Content-Disposition: inline; filename=".basename($filename));
readfile($filename,"r");
die();
}

function saveFeed($filename="",$displayContents=true){
if($filename==""){
$filename=$this->_generateFilename();
}
$FeedFile=fopen($filename,"w+");
if($FeedFile){
fputs($FeedFile,$this->createFeed());
fclose($FeedFile);
if($displayContents){
$this->_redirect($filename);
}
}else{
echo "
Error creating Feed file,please check write permissions.
";
}
}
}

class FeedDate{
var $unix;
function FeedDate($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($matches[7],1)=='+' OR substr($matches[7],1)=='-'){
$tzOffset=(substr($matches[7],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") && $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 += $tzOffset;
return;
}
if(preg_match("~(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})(.)~",$matches)){
$this->unix=mktime($matches[4],$matches[2],$matches[3],$matches[1]);
if(substr($matches[7],-2)) * 60;
}else{
if($matches[7]=="Z"){
$tzOffset=0;
}
}
$this->unix += $tzOffset;
return;
}
$this->unix=0;
}

function rfc822(){
$date=gmdate("Y-m-d H:i:s",$this->unix);
if(TIME_ZONE!="") $date .= " ".str_replace(":","",TIME_ZONE);
return $date;
}

function iso8601(){
$date=gmdate("Y-m-d H:i:s",$this->unix);
$date=substr($date,22) . ':' . substr($date,-2);
if(TIME_ZONE!="") $date=str_replace("+00:00",TIME_ZONE,$date);
return $date;
}

function unix(){
return $this->unix;
}
}

class RSSCreator10 extends FeedCreator{
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";
$Feed.= " ".htmlspecialchars($this->title)."\n";
$Feed.= " ".htmlspecialchars($this->description)."\n";
$Feed.= " ".$this->link."\n";
if($this->image!=null){
$Feed.= " <image rdf:resource=\"".$this->image->url."\" />\n";
}
$now=new FeedDate();
$Feed.= " ".htmlspecialchars($now->iso8601())."</dc:date>\n";
$Feed.= " \n";
$Feed.= " \n";
for ($i=0;$i<count($this->items);$i++){
$Feed.= " <rdf:li rdf:resource=\"".htmlspecialchars($this->items[$i]->link)."\"/>\n";
}
$Feed.= " </rdf:Seq>\n";
$Feed.= " \n";
$Feed.= " \n";
if($this->image!=null){
$Feed.= " <image rdf:about=\"".$this->image->url."\">\n";
$Feed.= " ".$this->image->title."\n";
$Feed.= " ".$this->image->link."\n";
$Feed.= " ".$this->image->url."\n";
$Feed.= " \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.= " Posting</dc:type>\n";
$Feed.= " text/html</dc:format>\n";
if($this->items[$i]->date!=null){
$itemDate=new FeedDate($this->items[$i]->date);
$Feed.= " ".htmlspecialchars($itemDate->iso8601())."</dc:date>\n";
}
if($this->items[$i]->source!=""){
$Feed.= " ".htmlspecialchars($this->items[$i]->source)."</dc:source>\n";
}
if($this->items[$i]->author!=""){
$Feed.= " ".htmlspecialchars($this->items[$i]->author)."</dc:creator>\n";
}
$Feed.= " ".htmlspecialchars(strip_tags(strtr($this->items[$i]->title,"\n\r"," ")))."\n";
$Feed.= " ".htmlspecialchars($this->items[$i]->link)."\n";
$Feed.= " ".htmlspecialchars($this->items[$i]->description)."\n";
$Feed.= $this->_createAdditionalElements($this->items[$i]->additionalElements," ");
$Feed.= " \n";
}
$Feed.= "</rdf:RDF>\n";
return $Feed;
}
}

class RSSCreator091 extends FeedCreator{
var $RSSVersion;

function RSSCreator091(){
$this->_setRSSVersion("0.91");
$this->contentType="application/RSS+xml";
}

function _setRSSVersion($version){
$this->RSSVersion=$version;
}

function createFeed(){
$Feed="<?xml version=\"1.0\" encoding=\"".$this->encoding."\"?>\n";
$Feed.= $this->_createGeneratorComment();
$Feed.= $this->_createStylesheetReferences();
$Feed.= "<rss version=\"".$this->RSSVersion."\">\n";
$Feed.= " \n";
$Feed.= " ".<a href="/tag/Feed/" target="_blank" class="keywords">Feed</a>Creator::iTrunc(htmlspecialchars($this->title),100)."\n";
$this->descriptionTruncSize=500;
$Feed.= " ".$this->getDescription()."\n";
$Feed.= " ".$this->link."\n";
$now=new FeedDate();
$Feed.= " ".htmlspecialchars($now->rfc822())."\n";
$Feed.= " ".FeedCREATOR_VERSION."\n";

if($this->image!=null){
$Feed.= " \n";
$Feed.= " ".$this->image->url."\n";
$Feed.= " ".<a href="/tag/Feed/" target="_blank" class="keywords">Feed</a>Creator::iTrunc(htmlspecialchars($this->image->title),100)."\n";
$Feed.= " ".$this->image->link."\n";
if($this->image->width!=""){
$Feed.= " ".$this->image->width."\n";
}
if($this->image->height!=""){
$Feed.= " ".$this->image->height."\n";
}
if($this->image->description!=""){
$Feed.= " ".$this->image->getDescription()."\n";
}
$Feed.= " \n";
}
if($this->language!=""){
$Feed.= " ".$this->language."\n";
}
if($this->copyright!=""){
$Feed.= " ".FeedCreator::iTrunc(htmlspecialchars($this->copyright),100)."\n";
}
if($this->editor!=""){
$Feed.= " ".FeedCreator::iTrunc(htmlspecialchars($this->editor),100)."\n";
}
if($this->webmaster!=""){
$Feed.= " ".FeedCreator::iTrunc(htmlspecialchars($this->webmaster),100)."\n";
}
if($this->pubDate!=""){
$pubDate=new FeedDate($this->pubDate);
$Feed.= " ".htmlspecialchars($pubDate->rfc822())."\n";
}
if($this->category!=""){
$Feed.= " ".htmlspecialchars($this->category)."\n";
}
if($this->docs!=""){
$Feed.= " ".FeedCreator::iTrunc(htmlspecialchars($this->docs),500)."\n";
}
if($this->ttl!=""){
$Feed.= " ".htmlspecialchars($this->ttl)."\n";
}
if($this->rating!=""){
$Feed.= " ".FeedCreator::iTrunc(htmlspecialchars($this->rating),500)."\n";
}
if($this->skipHours!=""){
$Feed.= " ".htmlspecialchars($this->skipHours)."\n";
}
if($this->skipDays!=""){
$Feed.= " ".htmlspecialchars($this->skipDays)."\n";
}
$Feed.= $this->_createAdditionalElements($this->additionalElements," ");

for ($i=0;$i<count($this->items);$i++){
$Feed.= " \n";
$Feed.= " ".<a href="/tag/Feed/" target="_blank" class="keywords">Feed</a>Creator::iTrunc(htmlspecialchars(strip_tags($this->items[$i]->title)),100)."\n";
$Feed.= " ".htmlspecialchars($this->items[$i]->link)."\n";
$Feed.= " ".$this->items[$i]->getDescription()."\n";

if($this->items[$i]->author!=""){
$Feed.= " ".htmlspecialchars($this->items[$i]->author)."\n";
}
/
// on hold
if($this->items[$i]->source!=""){
$feed.= " ".htmlspecialchars($this->items[$i]->source)."\n";
}
/
if($this->items[$i]->category!=""){
$feed.= " ".htmlspecialchars($this->items[$i]->category)."\n";
}
if($this->items[$i]->comments!=""){
$feed.= " ".htmlspecialchars($this->items[$i]->comments)."\n";
}
if($this->items[$i]->date!=""){
$itemDate=new FeedDate($this->items[$i]->date);
$feed.= " ".htmlspecialchars($itemDate->rfc822())."\n";
}
if($this->items[$i]->guid!=""){
$feed.= " ".htmlspecialchars($this->items[$i]->guid)."\n";
}
$feed.= $this->_createAdditionalElements($this->items[$i]->additionalElements," ");
$feed.= " \n";
}
$feed.= " \n";
$feed.= "\n";
return $feed;
}
}

class RSSCreator20 extends RSSCreator091{

function RSSCreator20(){
parent::_setRSSVersion("2.0");
}
}

使用示例：
<div class="codetitle"><a style="CURSOR: pointer" data="28151" class="copybut" id="copybut28151" onclick="doCopy('code28151')"> 代码如下:

php生成RSS订阅的方法

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