PHP 获取远程文件内容的代码，后面有一些注释可以参考下，其实大家可以参考脚本之家发布的一些采集程序代码。

如下函数：

 
<? 
/** 
获取远程文件内容 
@param $url 文件http地址 
*/ 
function fopen_url($url) 
{ 
if (function_exists('file_get_contents')) { 
$file_content = @file_get_contents($url); 
} elseif (ini_get('allow_url_fopen') && ($file = @fopen($url, 'rb'))){ 
$i = 0; 
while (!feof($file) && $i++ < 1000) { 
$file_content .= strtolower(fread($file, 4096)); 
} 
fclose($file); 
} elseif (function_exists('curl_init')) { 
$curl_handle = curl_init(); 
curl_setopt($curl_handle, CURLOPT_URL, $url); 
curl_setopt($curl_handle, CURLOPT_CONNECTTIMEOUT,2); 
curl_setopt($curl_handle, CURLOPT_RETURNTRANSFER,1); 
curl_setopt($curl_handle, CURLOPT_FAILONERROR,1); 
curl_setopt($curl_handle, CURLOPT_USERAGENT, 'Trackback Spam Check'); //引用垃圾邮件检查 
$file_content = curl_exec($curl_handle); 
curl_close($curl_handle); 
} else { 
$file_content = ''; 
} 
return $file_content; 
} 
?> 

相关解释：
1,ini_get : Returns the value of the configuration option as a string on success, or an empty string on failure(读取 php.ini 配置文件中的值)
2,; Whether to allow the treatment of URLs (like http:// or ftp://) as files.
allow_url_fopen = On(配置文件中的内容)
3,fopen( "rb"): 在操作二进制文件时如果没有指定 'b' 标记，可能会碰到一些奇怪的问题，包括坏掉的图片文件以及关于 \r\n 字符的奇怪问题。
注意: 为移植性考虑，强烈建议在用 fopen() 打开文件时总是使用 'b' 标记。
注意: 再一次，为移植性考虑，强烈建议你重写那些依赖于 't' 模式的代码使其使用正确的行结束符并改成 'b' 模式。
4,strtolower -- Make a string lowercase
5,curl_init() :curl_init -- Initialize a cURL session(初始化一个cUrl会话)
resource curl_init ( [string url] )
Initializes a new session and return a cURL handle for use with the curl_setopt(), curl_exec(), and curl_close() functions.
url--If provided, the CURLOPT_URL option will be set to its value. You can manually set this using the curl_setopt() function.
Returns a cURL handle on success, FALSE on errors.
6,curl_setopt -- Set an option for a cURL transfer(提供设置)
bool curl_setopt ( resource ch, int option, mixed value )
Sets an option on the given cURL session handle. (具体请看 PHP 手册) There:
CURLOPT_URL ：The URL to fetch. You can also set this when initializing a session with curl_init().
CURLOPT_CONNECTTIMEOUT ：The number of seconds to wait whilst trying to connect. Use 0 to wait indefinitely.(无限期等待 设置为 0)
CURLOPT_RETURNTRANSFER ：TRUE to return the transfer as a string of the return value of curl_exec() instead of outputting it out directly.
CURLOPT_FAILONERROR ：TRUE to fail silently if the HTTP code returned is greater than or equal to 400. The default behavior is to return the page normally, ignoring the code.
CURLOPT_USERAGENT ：The contents of the "User-Agent: " header to be used in a HTTP request.
7,curl_exec : Perform a cURL session, This function should be called after you initialize a cURL session and all the options for the session are set.
如果成功则返回 TRUE，失败则返回 FALSE。 However, if the CURLOPT_RETURNTRANSFER option is set, it will return the result on success, FALSE on failure
8,curl_close -- Close a cURL session

下面是一些参考代码:
PHP 采集程序 常用函数
PHP 采集获取指定网址的内容