$_SERVER['SERVER_NAME'] gives teh value of the server name as defined in host configuration (i.e for Apache the Apache .conf file).
Thus, it prints:
SERVER_NAME = domain.com
Note that the slash does not have to end.
Place the slash like this:
<?php include ($current . '/includes/mysection.php') ?>
When using the $_SERVER['SERVER_NAME'] variable in an apache virtual host setup with a ServerAlias directive, be sure to check the UseCanonicalName apache directive. If it is On, this variable will always have the apache ServerName value. If it is Off, it will have the value given by the headers sent by the browser.
Depending on what you want to do the content of this variable, put in On or Off.
Font: http://www.php.net/manual/en/reserved.variables.server.php
Font: PHP: $_SERVER variables: $_SERVER['HTTP_HOST'] vs $_SERVER['SERVER_NAME']