in Core Php to hide warning message set error_reporting(0) at top of common include file or individual file.
In Wordpress hide Warnings and Notices add following code in wp-config.php file
ini_set('log_errors','On');
ini_set('display_errors','Off');
ini_set('error_reporting', E_ALL );
define('WP_DEBUG', false);
define('WP_DEBUG_LOG', true);
define('WP_DEBUG_DISPLAY', false);