PHP warnings and notices are nothing to worry about on a production site most of the time Some of these can even be generated because the developer has to keep compatibility with older versions of WordPress as well as older PHP versions.
Lets find the best solutions for this
If you simply set WP_DEBUG to false in your wp-config.php file you should be fine. These don’t affect your site in any way.
However, the problem is that some times the above does not work.
That can happen most times on cheap shared hosts that force displaying PHP warnings and notices.
In that case, you can replace this line from your wp-config.php file:
define('WP_DEBUG', false);ini_set('display_errors','Off');
ini_set('error_reporting', E_ALL );
define('WP_DEBUG', false);
define('WP_DEBUG_DISPLAY', false);