    public static function is_email($vars){
        
        if(isset($_GET['act']) && $_GET['act'] == 'edit'){
            $id = Typo::int($_GET['id']);
            $where = "AND `id` != '{$id}' ";
        }else{
            $where = '';
        }
        $vars = sprintf('%s', Typo::cleanX($vars));
        $sql = sprintf("SELECT * FROM `user` WHERE `email` = '%s' %s", $vars, $where );
        $e = Db::result($sql);
        if(Db::$num_rows > 0){
            return false;
        }else{
            return true;
        }
    }

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.