MyBB Community Forums

I'm getting

Warning [2] Cannot modify header information - headers already sent by (output started at /home/domain/public_html/forum/inc/config.php:24) - Line: 1721 - File: inc/functions.php PHP 5.4.32 (Linux)

What is wrong with it? Here's my /inc/config.php page

<?php
$config['database']['type'] = 'mysql';
$config['database']['database'] = 'domain_forum';
$config['database']['table_prefix'] = 'forum_';
$config['database']['hostname'] = 'localhost';
$config['database']['username'] = 'domain_MyBB';
$config['database']['password'] = 'password';
$config['admin_dir'] = 'admin';
$config['hide_admin_links'] = 0;
$config['cache_store'] = 'db';
$config['memcache']['host'] = 'localhost';
$config['memcache']['port'] = 11211;
$config['super_admins'] = '1';
$config['database']['encoding'] = 'utf8';
$config['log_pruning'] = array(
 'admin_logs' => 365, // Administrator logs
 'mod_logs' => 365, // Moderator logs
 'task_logs' => 30, // Scheduled task logs
 'mail_logs' => 180, // Mail error logs
 'user_mail_logs' => 180, // User mail logs
 'promotion_logs' => 180 // Promotion logs
);
?>
                            

file content should end with ?> there should be no blank spaces & blank lines after it
if the warning persists you can simply remove ?> and check