如何使用php下载文件，提供的路径是已知的

$ch = curl_init ($url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_BINARYTRANSFER,1);
$rawdata = curl_exec($ch);
curl_close ($ch);
if(file_exists($fullpath)){
    unlink($fullpath);
}
$fp = fopen($fullpath,'x');
fwrite($fp, $rawdata);
fclose($fp);

$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);

http://www.php.net/manual/en/curl.examples-basic.php

或者使用这个（如果在PHP conf中设置了fopen包装器）：

$file = 'http://somehosted.com/file.pdf'; // URL to the file
$contents = file_get_contents($file); // read the remote file
touch('somelocal.pdf'); // create a local EMPTY copy
file_put_contents('somelocal.pdf', $contents); // put the fetchted data into the newly created file
// done :)

这个可能最适合你：http://www.jonasjohn.de/snippets/php/curl-example.htm