get_headers：发送服务器响应HTTP请求
get_headers(字符串url[链接格式])
get_headers()以数组的形式返回服务器HTTP请求。如果执行失败,将返回FALSE和一个错误的水平E_WARNING》。
可选参数设置为1,get_headers()能分析系统的响应速度和集数组中的键。

注意：使用该函数需要把 php.ini里面的allow_url_fopen = On，才能使用。

实例如下：
$url = http://www.ite5e.com;
print_r(get_headers($url));
print_r(get_headers($url, 1));
?>

打印结果：
Array

(<br>    [0] => HTTP/1.1 200 OK<br>    [1] => Connection: close<br>    [2] => Date: Tue, 16 Nov 2010 09:48:20 GMT<br>    [3] => Content-Length: 52708<br>    [4] => Content-Type: text/html<br>    [5] => Content-Location: http://www.ite5e.com/index.html<br>    [6] => Last-Modified: Tue, 16 Nov 2010 09:19:13 GMT<br>    [7] => Accept-Ranges: bytes<br>    [8] => ETag: "50d16c556f85cb1:b1f76"<br>    [9] => Server: Microsoft-IIS/6.0<br>    [10] => X-Powered-By: ASP.NET<br>)<br>Array<br>(<br>    [0] => HTTP/1.1 200 OK<br>    [Connection] => close<br>    [Date] => Tue, 16 Nov 2010 09:48:21 GMT<br>    [Content-Length] => 52708<br>    [Content-Type] => text/html<br>    [Content-Location] => http://www.ite5e.com/index.html<br>    [Last-Modified] => Tue, 16 Nov 2010 09:19:13 GMT<br>    [Accept-Ranges] => bytes<br>    [ETag] => "50d16c556f85cb1:b1f76"<br>    [Server] => Microsoft-IIS/6.0<br>    [X-Powered-By] => ASP.NET<br>)