    public static function header($vars = '')
    {
        header('Cache-Control: must-revalidate,max-age=300,s-maxage=900');
        $offset = 60 * 60 * 24 * 3;
        $ExpStr = 'Expires: '.gmdate('D, d M Y H:i:s', time() + $offset).' GMT';
        header($ExpStr);
        header('Content-Type: text/html; charset=utf-8');

        if (isset($vars)) {
            # code...
            $GLOBALS['data'] = $vars;
            self::theme('header', $vars);
        } else {
            self::theme('header');
        }
    }
The software constructs all or part of an SQL command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended SQL command when it is sent to a downstream component.