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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：
复制代码 代码如下:<?xml version="1.0" encoding="utf-8"?>
<rss version="2.0">
<channel>
<title>脚本之家</title>
<link>http://www.jb51.net/</link>
<description>脚本之家</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：
复制代码 代码如下:<?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."" --> ";
    }
 
    function _createAdditionalElements（$elements,$indentString=""）{
        $ae="";
        if（is_array（$elements））{
            foreach（$elements AS $key => $value）{
                $ae.= $indentString."<$key>$value</$key> ";
            }
        }
        return $ae;
    }
 
    function _createStylesheetReferences（）{
        $xml="";
        if（$this->cssStyleSheet） $xml .= "<?xml-stylesheet href="".$this->cssStyleSheet."" type="text/css"?> ";
        if（$this->xslStyleSheet） $xml .= "<?xml-stylesheet href="".$this->xslStyleSheet."" type="text/xsl"?> ";
        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.""?> ";
        $feed.= $this->_createGeneratorComment（）;
        if（$this->cssStyleSheet==""）{
            $cssStyleSheet="http://www.w3.org/2000/08/w3c-synd/style.css";
        }
        $feed.= $this->_createStylesheetReferences（）;
        $feed.= "<rdf:RDF ";
        $feed.= "    xmlns="http://purl.org/rss/1.0/" ";
        $feed.= "    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" ";
        $feed.= "    xmlns:slash="http://purl.org/rss/1.0/modules/slash/" ";
        $feed.= "    xmlns:dc="http://purl.org/dc/elements/1.1/"> ";
        $feed.= "    <channel rdf:about="".$this->syndicationURL.""> ";
        $feed.= "        <title>".htmlspecialchars（$this->title）."</title> ";
        $feed.= "        <description>".htmlspecialchars（$this->description）."</description> ";
        $feed.= "        <link>".$this->link."</link> ";
        if（$this->image！=null）{
            $feed.= "        <image rdf:resource="".$this->image->url."" /> ";
        }
        $now=new FeedDate（）;
        $feed.= "       <dc:date>".htmlspecialchars（$now->iso8601（））."</dc:date> ";
        $feed.= "        <items> ";
        $feed.= "            <rdf:Seq> ";
        for （$i=0;$i<count（$this->items）;$i++）{
            $feed.= "                <rdf:li rdf:resource="".htmlspecialchars（$this->items[$i]->link）.""/> ";
        }
        $feed.= "            </rdf:Seq> ";
        $feed.= "        </items> ";
        $feed.= "    </channel> ";
        if（$this->image！=null）{
            $feed.= "    <image rdf:about="".$this->image->url.""> ";
            $feed.= "        <title>".$this->image->title."</title> ";
            $feed.= "        <link>".$this->image->link."</link> ";
            $feed.= "        <url>".$this->image->url."</url> ";
            $feed.= "    </image> ";
        }
        $feed.= $this->_createAdditionalElements（$this->additionalElements,"    "）;
 
        for （$i=0;$i<count（$this->items）;$i++）{
            $feed.= "    <item rdf:about="".htmlspecialchars（$this->items[$i]->link）.""> ";
            //$feed.= "        <dc:type>Posting</dc:type> ";
            $feed.= "        <dc:format>text/html</dc:format> ";
            if（$this->items[$i]->date！=null）{
                $itemDate=new FeedDate（$this->items[$i]->date）;
                $feed.= "        <dc:date>".htmlspecialchars（$itemDate->iso8601（））."</dc:date> ";
            }
            if（$this->items[$i]->source！=""）{
                $feed.= "        <dc:source>".htmlspecialchars（$this->items[$i]->source）."</dc:source> ";
            }
            if（$this->items[$i]->author！=""）{
                $feed.= "        <dc:creator>".htmlspecialchars（$this->items[$i]->author）."</dc:creator> ";
            }
            $feed.= "        <title>".htmlspecialchars（strip_tags（strtr（$this->items[$i]->title," ","  "）））."</title> ";
            $feed.= "        <link>".htmlspecialchars（$this->items[$i]->link）."</link> ";
            $feed.= "        <description>".htmlspecialchars（$this->items[$i]->description）."</description> ";
            $feed.= $this->_createAdditionalElements（$this->items[$i]->additionalElements,"        "）;
            $feed.= "    </item> ";
        }
        $feed.= "</rdf:RDF> ";
        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.""?> ";
        $feed.= $this->_createGeneratorComment（）;
        $feed.= $this->_createStylesheetReferences（）;
        $feed.= "<rss version="".$this->RSSVersion.""> ";
        $feed.= "    <channel> ";
        $feed.= "        <title>".FeedCreator::iTrunc（htmlspecialchars（$this->title）,100）."</title> ";
        $this->descriptionTruncSize=500;
        $feed.= "        <description>".$this->getDescription（）."</description> ";
        $feed.= "        <link>".$this->link."</link> ";
        $now=new FeedDate（）;
        $feed.= "        <lastBuildDate>".htmlspecialchars（$now->rfc822（））."</lastBuildDate> ";
        $feed.= "        <generator>".FEEDCREATOR_VERSION."</generator> ";
 
        if（$this->image！=null）{
            $feed.= "        <image> ";
            $feed.= "            <url>".$this->image->url."</url> ";
            $feed.= "            <title>".FeedCreator::iTrunc（htmlspecialchars（$this->image->title）,100）."</title> ";
            $feed.= "            <link>".$this->image->link."</link> ";
            if（$this->image->width！=""）{
                $feed.= "            <width>".$this->image->width."</width> ";
            }
            if（$this->image->height！=""）{
                $feed.= "            <height>".$this->image->height."</height> ";
            }
            if（$this->image->description！=""）{
                $feed.= "            <description>".$this->image->getDescription（）."</description> ";
            }
            $feed.= "        </image> ";
        }
        if（$this->language！=""）{
            $feed.= "        <language>".$this->language."</language> ";
        }
        if（$this->copyright！=""）{
            $feed.= "        <copyright>".FeedCreator::iTrunc（htmlspecialchars（$this->copyright）,100）."</copyright> ";
        }
        if（$this->editor！=""）{
            $feed.= "        <managingEditor>".FeedCreator::iTrunc（htmlspecialchars（$this->editor）,100）."</managingEditor> ";
        }
        if（$this->webmaster！=""）{
            $feed.= "        <webMaster>".FeedCreator::iTrunc（htmlspecialchars（$this->webmaster）,100）."</webMaster> ";
        }
        if（$this->pubDate！=""）{
            $pubDate=new FeedDate（$this->pubDate）;
            $feed.= "        <pubDate>".htmlspecialchars（$pubDate->rfc822（））."</pubDate> ";
        }
        if（$this->category！=""）{
            $feed.= "        <category>".htmlspecialchars（$this->category）."</category> ";
        }
        if（$this->docs！=""）{
            $feed.= "        <docs>".FeedCreator::iTrunc（htmlspecialchars（$this->docs）,500）."</docs> ";
        }
        if（$this->ttl！=""）{
            $feed.= "        <ttl>".htmlspecialchars（$this->ttl）."</ttl> ";
        }
        if（$this->rating！=""）{
            $feed.= "        <rating>".FeedCreator::iTrunc（htmlspecialchars（$this->rating）,500）."</rating> ";
        }
        if（$this->skipHours！=""）{
            $feed.= "        <skipHours>".htmlspecialchars（$this->skipHours）."</skipHours> ";
        }
        if（$this->skipDays！=""）{
            $feed.= "        <skipDays>".htmlspecialchars（$this->skipDays）."</skipDays> ";
        }
        $feed.= $this->_createAdditionalElements（$this->additionalElements,"    "）;
 
        for （$i=0;$i<count（$this->items）;$i++）{
            $feed.= "        <item> ";
            $feed.= "            <title>".FeedCreator::iTrunc（htmlspecialchars（strip_tags（$this->items[$i]->title））,100）."</title> ";
            $feed.= "            <link>".htmlspecialchars（$this->items[$i]->link）."</link> ";
            $feed.= "            <description>".$this->items[$i]->getDescription（）."</description> ";
 
            if（$this->items[$i]->author！=""）{
                $feed.= "            <author>".htmlspecialchars（$this->items[$i]->author）."</author> ";
            }
            /*
             // on hold
             if（$this->items[$i]->source！=""）{
             $feed.= "            <source>".htmlspecialchars（$this->items[$i]->source）."</source> ";
             }
             */
            if（$this->items[$i]->category！=""）{
                $feed.= "            <category>".htmlspecialchars（$this->items[$i]->category）."</category> ";
            }
            if（$this->items[$i]->comments！=""）{
                $feed.= "            <comments>".htmlspecialchars（$this->items[$i]->comments）."</comments> ";
            }
            if（$this->items[$i]->date！=""）{
                $itemDate=new FeedDate（$this->items[$i]->date）;
                $feed.= "            <pubDate>".htmlspecialchars（$itemDate->rfc822（））."</pubDate> ";
            }
            if（$this->items[$i]->guid！=""）{
                $feed.= "            <guid>".htmlspecialchars（$this->items[$i]->guid）."</guid> ";
            }
            $feed.= $this->_createAdditionalElements（$this->items[$i]->additionalElements,"        "）;
            $feed.= "        </item> ";
        }
        $feed.= "    </channel> ";
        $feed.= "</rss> ";
        return $feed;
    }
}
 
class RSSCreator20 extends RSSCreator091{
 
    function RSSCreator20（）{
        parent::_setRSSVersion（"2.0"）;
    }
}
使用示例：
复制代码 代码如下:<?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="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.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。