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：

<?xml version="1.0" encoding="utf-8"?>
<rss version="2.0">
<channel>
<title></title>
<link>//www.jb51.net/</link>
<description></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.jb51.net");//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='//www.jb51.net/';
    $item->description =$rowbrs['description'];
    $rss->additem($item);
}
mysql_close($db);
$rss->savefeed("rss2.0","rss.xml");

希望本文所述对大家的php程序设计有所帮助。