Showing Cannot modify header information in php

Showing Cannot modify header information in php::

A PHP Error was encountered
Severity: Warning

Message: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\...)

Filename: libraries/Session.php

Line Number: 675


Solution:
Add at the start of the page or function:

ob_start();

Source:: http://stackofcodes.in/2018/01/05/showing-cannot-modify-header-information-php/