i want to upload a file in a way that user can see how many time is remaining from upload...with php and jquery $.ajax();
If you can't alter your server environment, use one of the Flash based uploading solutions like SWFUpload or Uploadify. (It's not possible to transmit files using pure Ajax as far as I know).
SWFUpload has a speed plugin that does exactly what you want, out of the box.
You may want to look into http://t.wits.sg/2008/06/25/howto-php-and-jquery-upload-progress-bar/
This might be what you are looking for http://www.uploadify.com/
if not some more information would be helpful, are you using http or ftp upload for starters.