A PHP Error was encountered

Severity: Notice

Message: Undefined index: HTTP_USER_AGENT

Filename: controllers/Main.php

Line Number: 18

Backtrace:

File: /var/www/html/application/controllers/Main.php
Line: 18
Function: _error_handler

File: /var/www/html/index.php
Line: 315
Function: require_once

Exercices Math Sn Secondaire 3