如果支持打开远程内容的选项的话，实际上php用fopen或file_get_contents都能获得一个网页的内容，但是默认的函数有个不足的地方就是无法获取http头，这在一些特殊的应用中很不方便，如，有一个链接：
http://www.abc.com/showvd.asp?id=18 
假如它返回的是一个图片，用默认函数就很难识别，但如果通过http应答头来判断就简单多了，此外如果对方通过 refer 来防盗链的话，也是无法获取的，用http类就能完美解决这些问题，而且速度也相差无几。
使用方法：
$hd = new dedehttpdown();
$hd->openurl(http://www.dedecms.com);
echo $hd->gethtml();
//如果保存为文件则用 $hd->savebin(dede.html);
$hd->close();
获得http请求头用
$hd->gethead(key)
设置请求头
$hd->sethead(key,value); (必须在调用 openurl 之前设定)
代码如下:
/* ---------------------------------------------------------------------
//织梦http下载类v1.0
//出自：织梦之旅 http://www.dedecms.com
//作者: it柏拉图
//时间: 2005-11-13 12:39
//声明: 首发在落伍者网站，转载请保留版权信息
--------------------------------------------------------------------- */
class dedehttpdown
{
        var $m_url = ;
        var $m_urlpath = ;
        var $m_scheme = http;
        var $m_host = ;
        var $m_port = 80;
        var $m_user = ;
        var $m_pass = ;
        var $m_path = /;
        var $m_query = ;
        var $m_fp = ;
        var $m_error = ;
        var $m_httphead =  ;
        var $m_html = ;
        var $m_puthead = ;
        var $baseurlpath = ;
        var $homeurl = ;
        var $jumpcount = 0;//防止多重重定向陷入死循环
        //
        //初始化系统
        //
        function privateinit($url)
        {
                        if($url==) return ;
                        $urls = ;
                        $urls = @parse_url($url);
                        $this->m_url = $url;
            if(is_array($urls))
            {
                          $this->m_host = $urls[host];
                          if(!empty($urls[scheme])) $this->m_scheme = $urls[scheme];
                          if(!empty($urls[user])){
                                        $this->m_user = $urls[user];
                          }
                          if(!empty($urls[pass])){
                                        $this->m_pass = $urls[pass];
                          }
                          if(!empty($urls[port])){
                                        $this->m_port = $urls[port];
                          }
                          if(!empty($urls[path])) $this->m_path = $urls[path];
                          $this->m_urlpath = $this->m_path;
                          if(!empty($urls[query])){
                                        $this->m_query = $urls[query];
                                        $this->m_urlpath .= ?.$this->m_query;
                          }
                          $this->homeurl = $urls[host];
                          $this->baseurlpath = $this->homeurl.$urls[path];
                          $this->baseurlpath = ereg_replace(/([^/]*)\.(.*)$,/,$this->baseurlpath);
                          $this->baseurlpath = ereg_replace(/$,,$this->baseurlpath);
                 }
        }
        //
        //打开指定网址
        //
        function openurl($url)
        {
                //重设各参数
                $this->m_url = ;
                $this->m_urlpath = ;
                $this->m_scheme = http;
                $this->m_host = ;
                $this->m_port = 80;
                $this->m_user = ;
                $this->m_pass = ;
                $this->m_path = /;
                $this->m_query = ;
                $this->m_error = ;
                $this->jumpcount = 0;
                $this->m_httphead = array() ;
                //$this->m_puthead = ;
                $this->m_html = ;
                $this->close();
                //初始化系统
                $this->privateinit($url);
                $this->privatestartsession();
        }
        //
        //打开303重定向网址
        //
        function jumpopenurl($url)
        {
                //重设各参数
                $this->m_url = ;
                $this->m_urlpath = ;
                $this->m_scheme = http;
                $this->m_host = ;
                $this->m_port = 80;
                $this->m_user = ;
                $this->m_pass = ;
                $this->m_path = /;
                $this->m_query = ;
                $this->m_error = ;
                $this->jumpcount++;
                $this->m_httphead = array() ;
                $this->m_html = ;
                $this->close();
                //初始化系统
                $this->privateinit($url);
                $this->privatestartsession();
        }
        //
        //获得某操作错误的原因
        //
        function printerror()
        {
                echo 错误信息：.$this->m_error;
                echo 具体返回头：
;
                foreach($this->m_httphead as $k=>$v)
                { echo $k => $v 
\r\n; }
        }
        //
        //判别用get方法发送的头的应答结果是否正确
        //
        function isgetok()
        {
                if( ereg(^2,$this->gethead(http-state)) )
                {        return true; }
                else
                {
                        $this->m_error .= $this->gethead(http-state). - .$this->gethead(http-describe).
;
                        return false;
                }
        }
        //
        //看看返回的网页是否是text类型
        //
        function istext()
        {
                if(ereg(^2,$this->gethead(http-state))
                        && eregi(^text,$this->gethead(content-type)))
                {        return true; }
                else
                {
                        $this->m_error .= 内容为非文本类型或网址重定向
;
                        return false;
                }
        }
        //
        //判断返回的网页是否是特定的类型
        //
        function iscontenttype($ctype)
        {
                if(ereg(^2,$this->gethead(http-state))
                        && $this->gethead(content-type)==strtolower($ctype))
                {        return true; }
                else
                {
                        $this->m_error .= 类型不对 .$this->gethead(content-type).
;
                        return false;
                }
        }
        //
        //用http协议下载文件
        //
        function savetobin($savefilename)
        {
                if(!$this->isgetok()) return false;
                if(@feof($this->m_fp)) { $this->m_error = 连接已经关闭！; return false; }
                $fp = fopen($savefilename,w);
                while(!feof($this->m_fp)){
                        fwrite($fp,fread($this->m_fp,1024));
                }
                fclose($this->m_fp);
                fclose($fp);
                return true;
        }
        //
        //保存网页内容为text文件
        //
        function savetotext($savefilename)
        {
                if($this->istext()) $this->savebinfile($savefilename);
                else return ;
        }
        //
        //用http协议获得一个网页的内容
        //
        function gethtml()
        {
                if(!$this->istext()) return ;
                if($this->m_html!=) return $this->m_html;
                if(!$this->m_fp||@feof($this->m_fp)) return ;
                while(!feof($this->m_fp)){
                        $this->m_html .= fgets($this->m_fp,256);
                }
                @fclose($this->m_fp);
                return $this->m_html;
        }
        //
        //开始http会话
        //
        function privatestartsession()
        {
                if(!$this->privateopenhost()){
                        $this->m_error .= 打开远程主机出错!;
                        return false;
                }
                if($this->gethead(http-edition)==http/1.1) $httpv = http/1.1;
                else $httpv = http/1.0;
                //发送固定的起始请求头get、host信息
                fputs($this->m_fp,get .$this->m_urlpath. $httpv\r\n);
                $this->m_puthead[host] = $this->m_host;
                //发送用户自定义的请求头
                if(!isset($this->m_puthead[accept])) { $this->m_puthead[accept] = */*; }
                if(!isset($this->m_puthead[user-agent])) { $this->m_puthead[user-agent] = mozilla/4.0 (compatible; msie 6.0; windows nt 5.2); }
                if(!isset($this->m_puthead[refer])) { $this->m_puthead[refer] = http://.$this->m_puthead[host]; }
                foreach($this->m_puthead as $k=>$v){
                        $k = trim($k);
                        $v = trim($v);
                        if($k!=&&$v!=){
                                fputs($this->m_fp,$k: $v\r\n);
                        }
                }
                //发送固定的结束请求头
                //http1.1协议必须指定文档结束后关闭链接,否则读取文档时无法使用feof判断结束
                if($httpv==http/1.1) fputs($this->m_fp,connection: close\r\n\r\n);
                else fputs($this->m_fp,\r\n);
                //获取应答头状态信息
                $httpstas = explode( ,fgets($this->m_fp,256));
                $this->m_httphead[http-edition] = trim($httpstas[0]);
                $this->m_httphead[http-state] = trim($httpstas[1]);
                $this->m_httphead[http-describe] = ;
                for($i=2;$i                        $this->m_httphead[http-describe] .=  .trim($httpstas[$i]);
                }
                //获取详细应答头
                while(!feof($this->m_fp)){
                        $line = trim(fgets($this->m_fp,256));
                        if($line == ) break;
                        $hkey = ;
                        $hvalue = ;
                        $v = 0;
                        for($i=0;$i                                if($v==1) $hvalue .= $line[$i];
                                if($line[$i]==:) $v = 1;
                                if($v==0) $hkey .= $line[$i];
                        }
                        $hkey = trim($hkey);
                        if($hkey!=) $this->m_httphead[strtolower($hkey)] = trim($hvalue);
                }
                //判断是否是3xx开头的应答
                if(ereg(^3,$this->m_httphead[http-state]))
                {
                        if($this->jumpcount > 3) return;
                        if(isset($this->m_httphead[location])){
                                $newurl = $this->m_httphead[location];
                                if(eregi(^http,$newurl)){
                                        $this->jumpopenurl($newurl);
                                }
                                else{
                                        $newurl = $this->fillurl($newurl);
                                        $this->jumpopenurl($newurl);
                                }
                        }
                        else
                        {        $this->m_error = 无法识别的转移应答！; }
                }//
        }
        //
        //获得一个http头的值
        //
        function gethead($headname)
        {
                $headname = strtolower($headname);
                if(isset($this->m_httphead[$headname]))
                        return $this->m_httphead[$headname];
                else
                        return ;
        }
        //
        //设置http头的值
        //
        function sethead($skey,$svalue)
        {
                $this->m_puthead[$skey] = $svalue;
        }
        //
        //打开连接
        //
        function privateopenhost()
        {
                if($this->m_host==) return false;
                $this->m_fp = @fsockopen($this->m_host, $this->m_port, &$errno, &$errstr,10);
                if(!$this->m_fp){
                        $this->m_error = $errstr;
                        return false;
                }
                else{
                        return true;
                }
        }
        //
        //关闭连接
        //
        function close(){
                @fclose($this->m_fp);
        }
        //
        //补全相对网址
        //
        function fillurl($surl)
  {
    $i = 0;
    $dstr = ;
    $pstr = ;
    $okurl = ;
    $pathstep = 0;
    $surl = trim($surl);
    if($surl==) return ;
    $pos = strpos($surl,#);
    if($pos>0) $surl = substr($surl,0,$pos);
    if($surl[0]==/){
            $okurl = http://.$this->homeurl./.$surl;
    }
    else if($surl[0]==.)
    {
      if(strlen($surl)      else if($surl[0]==/)
      {
              $okurl = http://.$this->baseurlpath./.substr($surl,2,strlen($surl)-2);
            }
      else{
        $urls = explode(/,$surl);
        foreach($urls as $u){
          if($u==..) $pathstep++;
          else if($i          else $dstr .= $urls[$i];
          $i++;
        }
        $urls = explode(/,$this->baseurlpath);
        if(count($urls)                 return ;
        else{
          $pstr = http://;
          for($i=0;$i          { $pstr .= $urls[$i]./; }
          $okurl = $pstr.$dstr;
        }
      }
    }
    else
    {
      if(strlen($surl)        $okurl = http://.$this->baseurlpath./.$surl;
      else if(strtolower(substr($surl,0,7))==http://)
        $okurl = $surl;
      else
        $okurl = http://.$this->baseurlpath./.$surl;
    }
    $okurl = eregi_replace(^(http://),,$okurl);
    $okurl = eregi_replace(/{1,},/,$okurl);
    return http://.$okurl;
  }
}
?> 以上就介绍了sock 发布一个用php fsockopen写的http下载的类，包括了sock方面的内容，希望对php教程有兴趣的朋友有所帮助。