why is unregister_setting() undefined?

That function is only available from the wp-admin section of the site. The file that contains it is only loaded as part of the wp-admin. You need to wrap it in a hook function: function unregister_users_can_register_setting() { unregister_setting(‘general’, ‘users_can_register’); } add_action(‘init’, ‘unregister_users_can_register_setting’);

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)