我有以下结构

otsg
 > class
   > authentication.php
   > database.php
   > user.php
 > include
   > config.inc.php
   > encryption.php
   > include.php
   > session.php
 > index.php
 > registration.php

include.php文件具有以下内容

ini_set('display_errors', 1);
error_reporting(E_ALL);

ini_set('include_path',ini_get('include_path').':/Applications/MAMP/htdocs/otsg/:');
require_once 'config.inc.php';
require_once '../class/database.php';
require_once '../class/user.php';
require_once 'encryption.php';
require_once 'session.php';
require_once '../class/authentication.php';

在index.php页面中，我包括了

require_once 'include/include.php';

当我打开页面index.php时，出现以下警告和致命错误。我不明白是什么原因导致此错误。当我给出绝对路径时，它可以工作。但是我相信绝对的路线不是一个好主意。

Warning: require_once(../class/database.php) [function.require-once]: failed to open stream: No such file or directory in /Applications/MAMP/htdocs/otsg/include/include.php on line 9

Fatal error: require_once() [function.require]: Failed opening required '../class/database.php' (include_path='.:/Applications/MAMP/bin/php5.3/lib/php:/Applications/MAMP/htdocs/otsg/include/:') in /Applications/MAMP/htdocs/otsg/include/include.php on line 9

提前致谢