本文實例講述了php生成RSS訂閱的方法。分享給大家供大家參考。具體分析如下：
    RSS（簡易信息聚合，也叫聚合內(nèi)容）是一種描述和同步網(wǎng)站內(nèi)容的格式。RSS可以是以下三個解釋的其中一個： Really Simple Syndication；RDF (Resource Description Framework) Site Summary； Rich Site Summary。但其實這三個解釋都是指同一種Syndication的技術(shù)。RSS目前廣泛用于網(wǎng)上新聞頻道，blog和wiki。使用RSS訂閱能更快地獲取信息，網(wǎng)站提供RSS輸出，有利于讓用戶獲取網(wǎng)站內(nèi)容的最新更新。網(wǎng)絡(luò)用戶可以在客戶端借助于支持RSS的聚合工具軟件，在不打開網(wǎng)站內(nèi)容頁面的情況下閱讀支持RSS輸出的網(wǎng)站內(nèi)容。
    從技術(shù)上來說一個RSS文件就是一段規(guī)范的XML數(shù)據(jù)，該文件一般以rss，xml或者rdf作為后綴，下面是一段 rss 文件的內(nèi)容示例：
    代碼如下:
    <?xml version="1.0" encoding="utf-8"?>
    <rss version="2.0">
    <channel>
    <title>腳本之家</title>
    <link>http://www.jb51.net/</link>
    <description>腳本之家</description>
    <item>
    <title>RSS Tutorial</title>
    <link>網(wǎng)站地址/rss</link>
    <description>New RSS tutorial on W3School</description>
    </item>
    <item>
    <title>XML Tutorial</title>
    <link>網(wǎng)站地址/xml</link>
    <description>New XML tutorial on W3School</description>
    </item>
    </channel>
    </rss>
    下面分享一段使用 php 動態(tài)生成 RSS 的代碼示例：
    代碼如下:
    <?php
    /**
    ** php 動態(tài)生成 RSS 類
    **/
    define("TIME_ZONE","");
    define("FEEDCREATOR_VERSION","您的網(wǎng)址
    class FeedItem extends HtmlDescribable{
    var $title,$description,$link;
    var $author,$authorEmail,$image,$category,$comments,$guid,$source,$creator;
    var $date;
    var $additionalElements=Array();
    }
    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;
    }
    $vars=get_object_vars($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};
    }
    }
    }
    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",$filename="",$timeout=3600){
    $this->_setFormat($format);
    $this->_feed->useCached($filename,$timeout);
    }
    }
    class FeedCreator extends HtmlDescribable{
    var $title,$description,$link;
    var $syndicationURL,$image,$language,$copyright,$pubDate,$lastBuildDate,$editor,$editorEmail,
    $webmaster,$category,$docs,$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,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)." ...";
    }
    function _createGeneratorComment(){
    return "<!-- generator=\"".FEEDCREATOR_VERSION."\" -->\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($fileInfo["basename"],0,-(strlen($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 useCached($filename="",$timeout=3600){
    $this->_timeout=$timeout;
    if($filename==""){
    $filename=$this->_generateFilename();
    }
    if(file_exists($filename) && (time()-filemtime($filename) < $timeout)){
    $this->_redirect($filename);
    }
    }
    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 "<br /><b>Error creating feed file, please check write permissions.</b><br />";
    }
    }
    }
    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+)?()){
    $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") && $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("~()){
    $this->unix=mktime($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;
    }
    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,0,22) . ':' . 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="";
    }
    $feed.= $this->_createStylesheetReferences();
    $feed.= "<rdf:RDF\n";
    $feed.= " xmlns=\"";
    $feed.= " xmlns:rdf=\"";
    $feed.= " xmlns:slash=\"";
    $feed.= " xmlns:dc=\"";
    $feed.= " <channel rdf:about=\"".$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;
    }
    }
    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.= " <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;
    }
    }
    class RSSCreator20 extends RSSCreator091{
    function RSSCreator20(){
    parent::_setRSSVersion("2.0");
    }
    }
    使用示例：
    代碼如下:
    <?php
    header('Content-Type:text/html; charset=utf-8');
    $db=mysql_connect('127.0.0.1','root','123456');
    mysql_query("set names utf8");
    mysql_select_db('dbname',$db);
    $brs=mysql_query('select * from article order by add_time desc limit 0,10',$db);
    $rss=new UniversalFeedCreator();
    $rss->title="頁面標題";
    $rss->link="網(wǎng)址http://";
    $rss->description="rss標題";
    while($rowbrs=mysql_fetch_array($brs)){
    $item=new FeedItem();
    $item->title =$rowbrs['subject'];
    $item->link='http://www.jb51.net/';
    $item->description =$rowbrs['description'];
    $rss->addItem($item);
    }
    mysql_close($db);
    $rss->saveFeed("RSS2.0","rss.xml");
    希望本文所述對大家的php程序設(shè)計有所幫助。