php curl流方式远程下载大文件

$url="http://*";
#下载文件
set_time_limit(0);
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,$url);
$fp =  fopen('./aa.zip', 'w+');
curl_setopt($ch, CURLOPT_FILE, $fp);
curl_exec ($ch);
curl_close ($ch);
fclose($fp);