Warning: Constant MULTISITE already defined in /var/www/html/wp-config.php on line 21

Warning: Cannot modify header information - headers already sent by (output started at /var/www/html/wp-config.php:21) in /var/www/html/wp-includes/pluggable.php on line 1450

Warning: Cannot modify header information - headers already sent by (output started at /var/www/html/wp-config.php:21) in /var/www/html/wp-includes/pluggable.php on line 1453