I used your code and it kicks back an error that the file can't be found at the URL specified, http://www.domainname/menu/about.php. Which is really funny because I can go directly to the include in a browser using the URL in the error.
It seems this code is returning the correct URL for the include but for some reason doesn't display.
<?php include($getPath . 'menu/about.php'); ?>
Note, I took out the / in front of menu because it is in $getPath