CodeIgniter加载session类 提示异常 如何解决

CodeIgniter加载session类 提示错误 怎么解决
A PHP Error was encountered

Severity: Warning

Message: Cannot modify header information - headers already sent by (output started at F:\APMServ5.2.6\www\htdocs\application\config\config.php:1)

Filename: libraries/Session.php

Line Number: 672



我的config.php的一部分代码：

PHP code

<!--

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--><?php if( !defined('BASEPATH') ) exit('No direct script access allowed');
/*
|--------------------------------------
| Base Site URL
|--------------------------------------
|
| URL to your CodeIgniter root. Typically this will be your base URL,
| WITH a trailing slash:
|
|    http://example.com/
|
| If this is not set then CodeIgniter will guess the protocol, domain and
| path to your installation.
|
*/
$config['base_url']    = '';

/*
|--------------------------------------
| Index File
|--------------------------------------
|
| Typically this will be your index.php file, unless you've renamed it to
| something else. If you are using mod_rewrite to remove the page set this
| variable so that it is blank.
|
*/
$config['index_page'] = 'index.php';

/*
|--------------------------------------
| URI PROTOCOL
|--------------------------------------

求高手解答

------解决方案--------------------
config.php 首行是空行？