php如何只抓取网页头

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php如何只抓取网页头？

php获取网页header信息的4种方法

php获取网页header信息的方法多种多样，就php语言来说，我知道的方法有4种, 下面逐一献上。

方法一：使用get_headers()函数

推荐指数:

get_header方法最简单只要两行代码即可搞定。如下：

$thisurl = "http://www.lao8.org/";
print_r(get_headers($thisurl, 1));

得到的结果为：

Array
(
    [0] => HTTP/1.1 200 OK
    [Cache-Control] => max-age=86400
    [Content-Length] => 76102
    [Content-Type] => text/html
    [Content-Location] => http://www.lao8.org/index.html
    [Last-Modified] => Fri, 19 Jul 2013 03:52:30 GMT
    [Accept-Ranges] => bytes
    [ETag] => "50bc48643384ce1:5cb3"
    [Server] => Microsoft-IIS/6.0
    [X-Powered-By] => ASP.NET
    [Date] => Fri, 19 Jul 2013 09:06:39 GMT
    [Connection] => close
)

方法二：使用http_response_header

推荐指数:

http_response_headerf方法也很简单，仅三行：

$thisurl = "http://www.lao8.org";
$html = file_get_contents($thisurl ); 
print_r($http_response_header);

得到的结果为：

Array
(
    [0] => HTTP/1.1 200 OK
    [1] => Cache-Control: max-age=86400
    [2] => Content-Length: 76102
    [3] => Content-Type: text/html
    [4] => Content-Location: http://www.lao8.org/index.html
    [5] => Last-Modified: Fri, 19 Jul 2013 03:52:30 GMT
    [6] => Accept-Ranges: bytes
    [7] => ETag: "50bc48643384ce1:5cb3"
    [8] => Server: Microsoft-IIS/6.0
    [9] => X-Powered-By: ASP.NET
    [10] => Date: Fri, 19 Jul 2013 09:06:41 GMT
    [11] => Connection: close
)

方法三：使用stream_get_meta_data()函数

推荐指数:

使用stream_get_meta_data()代码也只需三行：

$thisurl = "http://www.lao8.org/";
$fp = fopen($thisurl, 'r'); 
print_r(stream_get_meta_data($fp));

得到的结果为：

Array
(
    [wrapper_data] => Array
        (
            [0] => HTTP/1.1 200 OK
            [1] => Cache-Control: max-age=86400
            [2] => Content-Length: 76102
            [3] => Content-Type: text/html
            [4] => Content-Location: http://www.lao8.org/index.html
            [5] => Last-Modified: Fri, 19 Jul 2013 03:52:30 GMT
            [6] => Accept-Ranges: bytes
            [7] => ETag: "50bc48643384ce1:5cb3"
            [8] => Server: Microsoft-IIS/6.0
            [9] => X-Powered-By: ASP.NET
            [10] => Date: Fri, 19 Jul 2013 09:06:41 GMT
            [11] => Connection: close
        )
    [wrapper_type] => http
    [stream_type] => tcp_socket
    [mode] => r+
    [unread_bytes] => 1086
    [seekable] => 
    [uri] => http://www.lao8.org/
    [timed_out] => 
    [blocked] => 1
    [eof] => 
)

第四种方法: 使用php的高级函数 CURL()来获取

推荐指数:

上面的三种方法能获取一般的网页header信息，如果想要获取更详细的header信息比如网页是否启用了GZip压缩。这时候可以用php的高级函数curl()来获取。

使用curl获得header可以检测GZip压缩

先贴出代码：

<?php
$szUrl = 'http://www.lao8.org/';
$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, $szUrl);
curl_setopt($curl, CURLOPT_HEADER, 1);  //输出header信息
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);  //不显示网页内容
curl_setopt($curl, CURLOPT_ENCODING, ''); //允许执行gzip
$data=curl_exec($curl); 
if(!curl_errno($curl))
{
    $info = curl_getinfo($curl);
    $httpHeaderSize = $info['header_size'];  //header字符串体积
    $pHeader = substr($data, 0, $httpHeaderSize); //获得header字符串
    $split   = array("rn", "n", "r");  //需要格式化header字符串
    $pHeader = str_replace($split, '<br>', $pHeader); //使用<br>换行符格式化输出到网页上
    echo $pHeader;
}
?>

输出结果如下：

HTTP/1.1 200 OK
Cache-Control: max-age=86400
Content-Length: 15189
Content-Type: text/html
Content-Encoding: gzip
Content-Location: http://www.lao8.org/index.html
Last-Modified: Fri, 19 Jul 2013 03:52:28 GMT
Accept-Ranges: bytes
ETag: "0268633384ce1:5cb3"
Vary: Accept-Encoding
Server: Microsoft-IIS/6.0
X-Powered-By: ASP.NET
Date: Fri, 19 Jul 2013 09:27:21 GMT

可以看到使用curl获取到的header信息多了这行：Content-Encoding: gzip，网页启用了GZip压缩。

推荐学习：《PHP视频教程》

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