CI_Session_files_driver Error

Haii All,
Iam using Codeigniter v3, and angularjs.
my application was getting this below error in randomly. How to solve this issue.

Class CI_Session_files_driver contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (SessionHandlerInterface::open)

Fatal error: Class CI_Session_files_driver contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (SessionHandlerInterface::open) in E:xampphtdocstbookingsystemlibrariesSessiondriversSession_files_driver.php on line 49
A PHP Error was encountered
Severity: Error

Message: Class CI_Session_files_driver contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (SessionHandlerInterface::open)

Filename: drivers/Session_files_driver.php

Line Number: 49

Backtrace:

Source: AngularJS