At the head of your page



define('IN_PHPBB', true);
define('PHPBB_ROOT_PATH', './phpBB3/');

$phpbb_root_path = 'phpBB3/';

$phpEx = substr(strrchr(__FILE__, '.'), 1);
include($phpbb_root_path . 'common.' . $phpEx);
include($phpbb_root_path . 'includes/functions_display.' . $phpEx);

// Start session management
$user->session_begin();
$auth->acl($user->data);




The actual Login/Logout box:



           /* Start Logout*/
                     if ($user->data['is_registered']){
                     echo("<form method='post' action='".$phpbb_root_path."ucp.php?mode=logout&sid=".$user->data['session_id']."'>");
                     echo("<input type='submit' name='logout' value='Logout'>");
         echo("<input type='hidden' name='redirect' value='../index.php'>");
                     echo("<br /></form>");
                     }
                    /*End Logout*/

                     /*Start Login Box*/
                     if (!$user->data['is_registered']){
                                echo("form method='post' action='".$phpbb_root_path."ucp.php?mode=login'>");
                                echo(" Username:");
                                echo("<br />");
                                echo(" <input type='text' name='username' size='15' value=''>");
                                echo("<br /><br />");
                                echo(" Password:");
                                echo("<br />");
                                echo(" <input type='password' name='password' size='15' value=''>");
                                echo("<br /><br />");
                                echo("<input type='submit' name='login' value='Login'>");
                                echo("<input type='hidden' name='redirect' value='../".$_SERVER['PHP_SELF']."'>");
                                echo("<br /></form>");
                       }
                      /*End Login Box*/