codeigniter uri段无法正常工作，输出为0

localhost/backend/administrator/authentication/8218/0

在codeigniter中，我想获取这些值8218和0.

In codeigniter, I want to fetch these values 8218 and 0.

我的代码是:

class Administrator extends Controller {

function Administrator()
    {
            parent::Controller();
            $this->load->library('uri');
    }

function authentication()
    {        
        echo $seg1= $this->uri->segment(3);
        echo $seg2 = $this->uri->segment(4);
        echo $this->uri->total_segments(); 
    }

}

我没有得到任何输出，但是当我使用 $ this-> uri-> total_segments();

I am not getting any output, but I got out put as '0' when I used $this->uri->total_segments();

my config.php 

'AUTO'          Default - auto detects
| 'PATH_INFO'       Uses the PATH_INFO
| 'QUERY_STRING'    Uses the QUERY_STRING
| 'REQUEST_URI'     Uses the REQUEST_URI
| 'ORIG_PATH_INFO'  Uses the ORIG_PATH_INFO
|

$config['uri_protocol'] = "AUTO";

i am using .htaccess

<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteBase /backend/

    #Removes access to the system folder by users.
    #Additionally this will allow you to create a System.php controller,
    #previously this would not have been possible.
    #'system' can be replaced if you have renamed your system folder.
    RewriteCond %{REQUEST_URI} ^system.*
    RewriteRule ^(.*)$ /index.php?/$1 [L]    

    #When your application folder isn't in the system folder
    #This snippet prevents user access to the application folder
    #Submitted by: Fabdrol
    #Rename 'application' to your applications folder name.
    RewriteCond %{REQUEST_URI} ^application.*
    RewriteRule ^(.*)$ /index.php?/$1 [L]

    #Checks to see if the user is attempting to access a valid file,
    #such as an image or css document, if this isn't true it sends the
    #request to index.php
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^(.*)$ index.php?/$1 [L]
</IfModule>

<IfModule !mod_rewrite.c>
    # If we don't have mod_rewrite installed, all 404's
    # can be sent to index.php, and everything works as normal.
    # Submitted by: ElliotHaughin

    ErrorDocument 404 /index.php
</IfModule> 

任何人都能找出我的错误并建议我正确的代码.

Can any one find out my mistake and suggest me the correct code.