In local your server base is
$base= 'http://localhost';
and in server it should be
$base= 'http://www.cs.uml.edu/~USER_NAME/public_html/gameworld';
and final code
$base= 'http://www.cs.uml.edu/~USER_NAME/public_html/gameworld';
echo "
<ul class=navbar>
<li> <a href='$base/index.php'> Index </a> </li>
<li><a href='$base/src/devices/devices.php'>Devices</a></li>
<li><a href='$base/src/howto/howto.php'>How To</a></li>
</ul>
";