hide browser url in php?

Hi, I want to hide a dropbox link in a php. I managed to do this but I can not get it to work where I'm wrong.

<?php
<a href="mipaginaamostrar.php?mestra=1">
if($_GET['meustra']==1)
include ('https://dl.dropbox.com/s/1e2d600b8l8zmhi/muestra.txt');
?>