Wordpress - WP_DEBUG is not set, but I'm still getting warnings

Replace

define('WP_DEBUG', false);

with this:

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);

WP_DEBUG has no impact on PHP error output. In addition to error_reporting setting, set display_errors=0 in your php.ini file. It's enabled by default for development. But you'll want it off on production servers.

It is also possible, that this line is already set to false. In that case, you’ll see the following code:

define('WP_DEBUG', false);

In either case, you need to replace this line with the following code:

ini_set('display_errors','Off');
ini_set('error_reporting', E_ALL );
define('WP_DEBUG', false);
define('WP_DEBUG_DISPLAY', false);

Don’t forget to save your changes and upload your wp-config.php file back to the server.