A PHP Error was encountered

Severity: Notice

Message: Undefined index: HTTP_ACCEPT_LANGUAGE

Filename: models/Lang_model.php

Line Number: 54

Backtrace:

File: D:\web\ntueaa\application\models\Lang_model.php
Line: 54
Function: _error_handler

File: D:\web\ntueaa\application\models\Lang_model.php
Line: 31
Function: accept_language

File: D:\web\ntueaa\application\models\Cart_model.php
Line: 13
Function: get_lang

File: D:\web\ntueaa\application\controllers\Home.php
Line: 10
Function: model

File: D:\web\ntueaa\index.php
Line: 315
Function: require_once