http://php.net/manual/en/function.filesize.php#92462

然后执行此操作以获取文件：

$remote = fopen('remote-file','r');
$local = fopen('local-file','w');

$read_bytes = 0;
while(!feof($remote)) {
  $buffer = fread($remote,2048);
  fwrite($local,$buffer);

  $read_bytes += 2048;

  //Use $filesize as calculated earlier to get the progress percentage
  $progress = min(100,100 * $read_bytes / $filesize);
  //you'll need some way to send $progress to the browser.
  //maybe save it to a file and then let an Ajax call check it?
}
fclose($remote);
fclose($local);