get_mysql_var example

'private' => true,
        );

        $info['wp-database']['fields']['database_collate'] = array(
            'label'   => __( 'Database collation' ),
            'value'   => $wpdb->collate,
            'private' => true,
        );

        $info['wp-database']['fields']['max_allowed_packet'] = array(
            'label' => __( 'Max allowed packet size' ),
            'value' => self::get_mysql_var( 'max_allowed_packet' ),
        );

        $info['wp-database']['fields']['max_connections'] = array(
            'label' => __( 'Max connections number' ),
            'value' => self::get_mysql_var( 'max_connections' ),
        );

        // List must use plugins if there are any.         $mu_plugins = get_mu_plugins();

        foreach ( $mu_plugins as $plugin_path => $plugin ) {