I am using facebook comments and providing the url of the page to distinguish. here is the code I am using

PHP Code:
<?php $commenturl="http://".$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'];?>

<div id="fb-root"></div>
<script>(function(d, s, id) {
  var js, fjs = d.getElementsByTagName(s)[0];
  if (d.getElementById(id)) {return;}
  js = d.createElement(s); js.id = id;
  js.src = "//connect.facebook.net/en_US/all.js#xfbml=1";
  fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));</script>

<fb:comments href="<?php echo $commenturl?>" num_posts="8" width="670"></fb:comments>
My url is www.domain.com/foldername/index.php?etc.

so it shows up the comment feed ok, but once someone posts a comment the url on his wall omits the foldername and directly goes to mangoestv.com/index.php?etc.

what am I supposed to do?