A PHP Error was encountered

Severity: Notice

Message: Undefined variable: login_url

Filename: views/header.php

Line Number: 35

Backtrace:

File: /var/www/html/application/views/header.php
Line: 35
Function: _error_handler

File: /var/www/html/application/views/details_subs_v.php
Line: 1
Function: view

File: /var/www/html/application/controllers/Book.php
Line: 337
Function: view

File: /var/www/html/index.php
Line: 299
Function: require_once