Curl采摘乱码与采集不到PHP

Curl 采集乱码与采集不到 PHP
PHP程序是用gbk2312编码的：

$url = "http://www.sina.com.cn";//gbk2312编码
//$url = "http://www.163.com";//gbk2312编码
//$url = "http://www.sohu.com";//gbk2312编码


$ch = curl_init($url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER , true);//返回获取的输出的文本流
$ret = curl_exec($ch);
curl_setopt($ch, CURLOPT_TIMEOUT, 1);
curl_close($ch);
echo $ret;

?>

在采集sina.com.cn时，是正常的，但是采集163.com时是为空的，采集sohu.com时是丢码的.
这是怎么回事呢？如何解决？有哪位怎么呀？先谢谢了！！！没多少分了，不好意思。

------解决方案--------------------
别的不说,我就是来拿分的.楼主记得给全分

$curl=curl_init('http://www.163.com');

curl_setopt($curl,CURLOPT_RETURNTRANSFER,1);

curl_setopt($curl,CURLOPT_USERAGENT,'Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; SV1; .NET CLR 1.1.4322)');

$html=curl_exec($curl);

var_dump($html);





$curl=curl_init('http://www.sohu.com');

curl_setopt($curl,CURLOPT_RETURNTRANSFER,1);

curl_setopt($curl,CURLOPT_USERAGENT,'Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; SV1; .NET CLR 1.1.4322)');

$html=curl_exec($curl);

//$html=strstr($html,'<');

$html=gzdecode($html);

var_dump($html);





function gzdecode($data) {   

  $len = strlen($data);   

  if ($len < 18 
------解决方案--------------------
 strcmp(substr($data,0,2),"\x1f\x8b")) {   

   return null;  // Not GZIP format (See RFC 1952)   

  }   

  $method = ord(substr($data,2,1));  // Compression method   

  $flags  = ord(substr($data,3,1));  // Flags   

  if ($flags & 31 != $flags) {   

   // Reserved bits are set -- NOT ALLOWED by RFC 1952   

   return null;   

  }   

  // NOTE: $mtime may be negative (PHP integer limitations)   

  $mtime = unpack("V", substr($data,4,4));   

  $mtime = $mtime[1];   

  $xfl  = substr($data,8,1);   

  $os    = substr($data,8,1);   

  $headerlen = 10;   

  $extralen  = 0;   

  $extra    = "";   

  if ($flags & 4) {   

   // 2-byte length prefixed EXTRA data in header   

   if ($len - $headerlen - 2 < 8) {   

     return false;    // Invalid format   

   }   

   $extralen = unpack("v",substr($data,8,2));   

   $extralen = $extralen[1];