curl强制下载文件

<?php
function download_remote_file_with_curl($file_url, $save_to)
{
$ch = curl_init();
curl_setopt($ch, CURLOPT_POST, 0);
curl_setopt($ch,CURLOPT_URL,$file_url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$file_content = curl_exec($ch);
curl_close($ch);

$downloaded_file = fopen($save_to, 'w');
fwrite($downloaded_file, $file_content);
fclose($downloaded_file);

}
download_remote_file_with_curl('http://static.oschina.net/uploads/user/2/4873_50.jpg', 'file.jpg')
?>