migrations::up PHP Method

    public function up($to = null)
    {
        // sorted migration files
        $files = $this->files();
        if (is_null($to)) {
            $to = end(array_keys($files));
        }
        // run migrations
        foreach ($files as $num => $item) {
            // upto
            if ($num > $to) {
                break;
            }
            // starting from
            if ($num < $this->current) {
                continue;
            }
            // run
            require $item['path'];
            $m = new $item['class']();
            $m->up();
        }
        return $num;
    }