Cannot modify header information headers already sent error

If you are a wordpress user sometime you might end up facing error similar to this while logging in as an admin.

Warning: Cannot modify header information - headers already sent by (output started at /home/smarttra/public_html/vkslabs.com/wp-content/themes/news/functions.php:6) in /home/smarttra/public_html/vkslabs.com/wp-includes/pluggable.php on line 896

Possible fixes for this issue includes

1. Remove blank spaces before <? and after ?> in functions.php under wp-includes folder

2. Add ob_start(); as the first line right after <? in functions.php