The way you have this setup seems like it should work. Are you getting any errors on the page? When you say that the content does not show are you getting a blank white page? If so you may need to add some code to display errors on the page. Try putting this on the top of the page:
<?php
error_reporting(E_ALL);
ini_set('display_errors','on');
?>
Please let us know the result you are getting with this and if you have a link where we can see the problem that would also be helpful.