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如何抓取开了gzip的网页

2024-07-26 17:39:01   217人阅读

有时候用 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。

编码问题好办，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。繁峙县粮食局

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print?
1请求头信息原始头信息
2Accept  text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
3Accept-Encoding gzip, deflate
4Accept-Language zh-cn,zh;q=0.8,en-us;q=0.5,en;q=0.3
5Connection  keep-alive
6Cookie  __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
7Host    www.nowamagic.net
8User-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。

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print?
1$data = file_get_contents("compress.zlib://".$url);

2. 使用CURL代替file_get_contents

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1function curl_get($url, $gzip=false){
2    $curl = curl_init($url);
3    curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
4    curl_setopt($curl, CURLOPT_CONNECTTIMEOUT, 10);
5    if($gzip) curl_setopt($curl, CURLOPT_ENCODING, "gzip"); // 关键在这里
6    $content = curl_exec($curl);
7    curl_close($curl);
8    return $content;
9}

3. 使用gzip解压函数

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print?
001function gzdecode($data) {
002  $len = strlen($data);
003  if ($len < 18 || strcmp(substr($data,0,2),"\x1f\x8b")) {
004    return null;  // Not GZIP format (See RFC 1952)
005  }
006  $method = ord(substr($data,2,1));  // Compression method
007  $flags  = ord(substr($data,3,1));  // Flags
008  if ($flags & 31 != $flags) {
009    // Reserved bits are set -- NOT ALLOWED by RFC 1952
010    return null;
011  }
012  // NOTE: $mtime may be negative (PHP integer limitations)
013  $mtime = unpack("V", substr($data,4,4));
014  $mtime = $mtime[1];
015  $xfl   = substr($data,8,1);
016  $os    = substr($data,8,1);
017  $headerlen = 10;
018  $extralen  = 0;
019  $extra     = "";
020  if ($flags & 4) {
021    // 2-byte length prefixed EXTRA data in header
022    if ($len - $headerlen - 2 < 8) {
023      return false;    // Invalid format
024    }
025    $extralen = unpack("v",substr($data,8,2));
026    $extralen = $extralen[1];
027    if ($len - $headerlen - 2 - $extralen < 8) {
028      return false;    // Invalid format
029    }
030    $extra = substr($data,10,$extralen);
031    $headerlen += 2 + $extralen;
032  }
033 
034  $filenamelen = 0;
035  $filename = "";
036  if ($flags & 8) {
037    // C-style string file NAME data in header
038    if ($len - $headerlen - 1 < 8) {
039      return false;    // Invalid format
040    }
041    $filenamelen = strpos(substr($data,8+$extralen),chr(0));
042    if ($filenamelen === false || $len - $headerlen - $filenamelen - 1 < 8) {
043      return false;    // Invalid format
044    }
045    $filename = substr($data,$headerlen,$filenamelen);
046    $headerlen += $filenamelen + 1;
047  }
048 
049  $commentlen = 0;
050  $comment = "";
051  if ($flags & 16) {
052    // C-style string COMMENT data in header
053    if ($len - $headerlen - 1 < 8) {
054      return false;    // Invalid format
055    }
056    $commentlen = strpos(substr($data,8+$extralen+$filenamelen),chr(0));
057    if ($commentlen === false || $len - $headerlen - $commentlen - 1 < 8) {
058      return false;    // Invalid header format
059    }
060    $comment = substr($data,$headerlen,$commentlen);
061    $headerlen += $commentlen + 1;
062  }
063 
064  $headercrc = "";
065  if ($flags & 1) {
066    // 2-bytes (lowest order) of CRC32 on header present
067    if ($len - $headerlen - 2 < 8) {
068      return false;    // Invalid format
069    }
070    $calccrc = crc32(substr($data,0,$headerlen)) & 0xffff;
071    $headercrc = unpack("v", substr($data,$headerlen,2));
072    $headercrc = $headercrc[1];
073    if ($headercrc != $calccrc) {
074      return false;    // Bad header CRC
075    }
076    $headerlen += 2;
077  }
078 
079  // GZIP FOOTER - These be negative due to PHP‘s limitations
080  $datacrc = unpack("V",substr($data,-8,4));
081  $datacrc = $datacrc[1];
082  $isize = unpack("V",substr($data,-4));
083  $isize = $isize[1];
084 
085  // Perform the decompression:
086  $bodylen = $len-$headerlen-8;
087  if ($bodylen < 1) {
088    // This should never happen - IMPLEMENTATION BUG!
089    return null;
090  }
091  $body = substr($data,$headerlen,$bodylen);
092  $data = "";
093  if ($bodylen > 0) {
094    switch ($method) {
095      case 8:
096        // Currently the only supported compression method:
097        $data = gzinflate($body);
098        break;
099      default:
100        // Unknown compression method
101        return false;
102    }
103  } else {
104    // I‘m not sure if zero-byte body content is allowed.
105    // Allow it for now...  Do nothing...
106  }
107 
108  // Verifiy decompressed size and CRC32:
109  // NOTE: This may fail with large data sizes depending on how
110  //       PHP‘s integer limitations affect strlen() since $isize
111  //       may be negative for large sizes.
112  if ($isize != strlen($data) || crc32($data) != $datacrc) {
113    // Bad format!  Length or CRC doesn‘t match!
114    return false;
115  }
116  return $data;
117}

使用：

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print?
1$html=file_get_contents(‘http://www.nowamagic.net/librarys/veda/‘);
2$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。

如何抓取开了gzip的网页


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