用 file_get_contents() 函数抓取网页会发生乱码现象。有两个原因会导致乱码，一个是编码问题，一个是目标页面开了Gzip，下面说的就是开了Gzip功能如何才能不乱码的方法

把抓取到的内容转下编码即可($content=iconv("GBK", "UTF-8//IGNORE", $content);)，我们这里讨论的是如何抓取开了Gzip的页面。怎么判断呢？获取的头部当中有Content-Encoding: gzip说明内容是GZIP压缩的。用FireBug看一下就知道页面开了gzip没有。下面是用firebug查看我的博客的头信息，Gzip是开了的。

请求头信息原始头信息
Accept text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Encoding gzip, deflate
Accept-Language zh-cn,zh;q=0.8,en-us;q=0.5,en;q=0.3
Connection keep-alive
Cookie __utma=225240837.787252530.1317310581.1335406161.1335411401.1537; __utmz=225240837.1326850415.887.3.utmcsr=google|utmccn=(organic)|utmcmd=organic|utmctr=%E4%BB%BB%E4%BD%95%E9%A1%B9%E7%9B%AE%E9%83%BD%E4%B8%8D%E4%BC%9A%E9%82%A3%E4%B9%88%E7%AE%80%E5%8D%95%20site%3Awww.nowamagic.net; PHPSESSID=888mj4425p8s0m7s0frre3ovc7; __utmc=225240837; __utmb=225240837.1.10.1335411401
Host www.nowamagic.net
User-Agent Mozilla/5.0 (Windows NT 5.1; rv:12.0) Gecko/20100101 Firefox/12.0

下面介绍一些解决方案：

1. 使用自带的zlib库
如果服务器已经装了zlib库，用下面的代码可以轻易解决乱码问题。

$data = file_get_contents("compress.zlib://".$url);

2. 使用CURL代替file_get_contents

function curl_get($url, $gzip=false){
 $curl = curl_init($url);
 curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
 curl_setopt($curl, CURLOPT_CONNECTTIMEOUT, 10);
 if($gzip) curl_setopt($curl, CURLOPT_ENCODING, "gzip"); // 关键在这里
 $content = curl_exec($curl);
 curl_close($curl);
 return $content;
}

3. 使用gzip解压函数

function gzdecode($data) { 
  $len = strlen($data); 
  if ($len < 18 || strcmp(substr($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 = $extralen[1]; 
    if ($len - $headerlen - 2 - $extralen < 8) { 
      return false;    // Invalid format 
    } 
    $extra = substr($data,10,$extralen); 
    $headerlen += 2 + $extralen; 
  } 

  $filenamelen = 0; 
  $filename = ""; 
  if ($flags & 8) { 
    // C-style string file NAME data in header 
    if ($len - $headerlen - 1 < 8) { 
      return false;    // Invalid format 
    } 
    $filenamelen = strpos(substr($data,8+$extralen),chr(0)); 
    if ($filenamelen === false || $len - $headerlen - $filenamelen - 1 < 8) { 
      return false;    // Invalid format 
    } 
    $filename = substr($data,$headerlen,$filenamelen); 
    $headerlen += $filenamelen + 1; 
  } 
  $commentlen = 0; 
  $comment = ""; 
  if ($flags & 16) { 
    // C-style string COMMENT data in header 
    if ($len - $headerlen - 1 < 8) { 
      return false;    // Invalid format 
    } 
    $commentlen = strpos(substr($data,8+$extralen+$filenamelen),chr(0)); 
    if ($commentlen === false || $len - $headerlen - $commentlen - 1 < 8) { 
      return false;    // Invalid header format 
    } 
    $comment = substr($data,$headerlen,$commentlen); 
    $headerlen += $commentlen + 1; 
  } 
  $headercrc = ""; 
  if ($flags & 1) { 
    // 2-bytes (lowest order) of CRC32 on header present 
    if ($len - $headerlen - 2 < 8) { 
      return false;    // Invalid format 
    } 
    $calccrc = crc32(substr($data,0,$headerlen)) & 0xffff; 
    $headercrc = unpack("v", substr($data,$headerlen,2)); 
    $headercrc = $headercrc[1]; 
    if ($headercrc != $calccrc) { 
      return false;    // Bad header CRC 
    } 
    $headerlen += 2; 
  } 
  // GZIP FOOTER - These be negative due to PHP's limitations 
  $datacrc = unpack("V",substr($data,-8,4)); 
  $datacrc = $datacrc[1]; 
  $isize = unpack("V",substr($data,-4)); 
  $isize = $isize[1]; 
  // Perform the decompression: 
  $bodylen = $len-$headerlen-8; 
  if ($bodylen < 1) { 
    // This should never happen - IMPLEMENTATION BUG! 
    return null; 
  } 
  $body = substr($data,$headerlen,$bodylen); 
  $data = ""; 
  if ($bodylen > 0) { 
    switch ($method) { 
      case 8: 
        // Currently the only supported compression method: 
        $data = gzinflate($body); 
        break; 
      default: 
        // Unknown compression method 
        return false; 
    } 
  } else { 
    // I'm not sure if zero-byte body content is allowed. 
    // Allow it for now...  Do nothing... 
  } 
  // Verifiy decompressed size and CRC32: 
  // NOTE: This may fail with large data sizes depending on how 
  //       PHP's integer limitations affect strlen() since $isize 
  //       may be negative for large sizes. 
  if ($isize != strlen($data) || crc32($data) != $datacrc) { 
    // Bad format!  Length or CRC doesn't match! 
    return false; 
  } 
  return $data; 
}

使用：

$html=file_get_contents('http://www.jb51.net/');
$html=gzdecode($html);

就介绍这三个方法，应该能解决大部分gzip引起的抓取乱码问题了。