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