php file_get_contents抓取Gzip网页乱码的三种解决方法

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('//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。