php生成RSS订阅示例

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：

<?xml version="1.0" encoding="utf-8"?>
<rss version="2.0">
<channel>
<title>php程序员教程网</title>
<link>http://www.maopiaopiao.com/</link>
<description>本站是一个php程序员的工作生活笔记!</description>
<item>
<title>RSS Tutorial</title>
<link>网站地址/rss</link>
<description>New RSS tutorial on W3School</description>
</item>
<item>
<title>XML Tutorial</title>
<link>网站地址/xml</link>
<description>New XML tutorial on W3School</description>
</item>
</channel>
</rss>

下面分享一段使用 php 动态生成 RSS 的代码示例：

<?php
/**
** php 动态生成 RSS 类
**/
define("TIME_ZONE","");
define("FEEDCREATOR_VERSION","www.maopiaopiao.com");//您的网址
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+)?(\\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") && $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;
    }

    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="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;
    }
}

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：

<?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="页面标题";
$rss->link="网址http://";
$rss->description="rss标题";
while($rowbrs=mysql_fetch_array($brs)){
    $item=new FeedItem();
    $item->title =$rowbrs['subject'];
    $item->link='http://www.maopiaopiao.com/';
    $item->description =$rowbrs['description'];
    $rss->addItem($item);
}
mysql_close($db);
$rss->saveFeed("RSS2.0","rss.xml");