PHP函数库里面，提到CURL，恐怕很多人都会翘起大拇指吧，确实，这个函数库太牛叉了
CURL其实是调用的CURL的lib,随着PHP版本的升高，curl所需的lib版本也随之提高。
关于CURL所必须的类库和安装说明，手册上有详细介绍：
Requirements
In order to use PHP's cURL functions you need to install the libcurl package. PHP requires that you use libcurl 7.0.2-beta or higher. In PHP 4.2.3, you will need libcurl version 7.9.0 or higher. From PHP 4.3.0, you will need a libcurl version that's 7.9.8 or higher. PHP 5.0.0 requires a libcurl version 7.10.5 or greater.
Installation
To use PHP's cURL support you must also compile PHP --with-curl[=DIR] where DIR is the location of the directory containing the lib and include directories. In the "include" directory there should be a folder named "curl" which should contain the easy.h and curl.h files. There should be a file named libcurl.a located in the "lib" directory. Beginning with PHP 4.3.0 you can configure PHP to use cURL for URL streams --with-curlwrappers.
Note to Win32 Users: In order to enable this module on a Windows environment, libeay32.dll and ssleay32.dll must be present in your PATH.
You don't need libcurl.dll from the cURL site.
然后在使用的时候也很方便，只需要初始化一下，设置一下postfields或者GET啥啥的，最后exec一下就行了。关键是别忘了close.
例子代码如下：
$ch = curl_init("http://www.example.com/");
$fp = fopen("example_homepage.txt", "w");
curl_setopt($ch, CURLOPT_FILE, $fp);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_exec($ch);
curl_close($ch);
fclose($fp);
以上例子代码有点特殊，是因为他把网页内容进行了下载，同时生成一个文件。这是默认调用GET的方法。
其实，CURL更多的是用来处理POST数据、上传文件等功能
例子如下：
<?
/*
* Author: Ron
* Released: August 4, 2007
* Description: An example of the disguise_curl() function in order to grab contents from a website while remaining fully camouflaged by using a fake user agent and fake headers.
*/
$url = 'http://www.ericgiguere.com/tools/http-header-viewer.html';
// disguises the curl using fake headers and a fake user agent.
function disguise_curl($url)
{
$curl = curl_init();
// Setup headers - I used the same headers from Firefox version 2.0.0.6
// below was split up because php.net said the line was too long. :/
$header[0] = "Accept: text/xml,application/xml,application/xhtml+xml,";
$header[0] .= "text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5";
$header[] = "Cache-Control: max-age=0";
$header[] = "Connection: keep-alive";
$header[] = "Keep-Alive: 300";
$header[] = "Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7";
$header[] = "Accept-Language: en-us,en;q=0.5";
$header[] = "Pragma: "; // browsers keep this blank.
curl_setopt($curl, CURLOPT_URL, $url);
curl_setopt($curl, CURLOPT_USERAGENT, 'Googlebot/2.1 (+http://www.google.com/bot.html)');
curl_setopt($curl, CURLOPT_HTTPHEADER, $header);
curl_setopt($curl, CURLOPT_REFERER, 'http://www.google.com');
curl_setopt($curl, CURLOPT_ENCODING, 'gzip,deflate');
curl_setopt($curl, CURLOPT_AUTOREFERER, true);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($curl, CURLOPT_TIMEOUT, 10);
$html = curl_exec($curl); // execute the curl command
curl_close($curl); // close the connection
return $html; // and finally, return $html
}
// uses the function and displays the text off the website
$text = disguise_curl($url);
echo $text;
?>
上面是一个比较完整的实现。特别需要注意的是header头部的发送，最初看手册的时候，我一以为CURLOPT_HTTPHEADER所需的数组是键值对应的，即：
$header = array('Keep-Alive'=>'300');
现实的残酷告诉我，不应该这么用，而是象上面的例子那样，每条header为数组的一个记录。
切记切记啊
