<?php header("Content-Type: text/html; charset=utf-8"); ?>
<?php $permittedList = array(
"action" =>
    array("upload", "delete"),
"owner" =>
    array("slider", "project")
); ?>
<?php
(
    (count($_GET) == 2) and
    (
        in_array($_GET['action'], $permittedList['action'])
        and
        in_array($_GET['owner'], $permittedList['owner'])
    )
) ?
require_once('includes/functions.php') :
exit(header('HTTP/1.1 403 Forbidden'));
?>