function force_download($file)

{

	if ((isset($file))&&(file_exists($file)))

	{

	        header("Content-length: ".filesize($file));

		header('Content-Type: application/octet-stream');

		header('Content-Disposition: attachment; filename="' . $file . '"');

		readfile("$file");

	}

	else

	{

		echo "No se ha seleccionado ningún fichero";

	}

 }