webman中递归方法的静态变量无限增长问题

public static function getSort($data, $pid = 0, $i = 0)
    {
        static $arr = array();
        if($i == 0){
            $arr = [];
        }
        foreach ($data as $k => $v) {
            if ($v['pid'] == $pid) {
                $arr[] = $v;
                $i++;
                self::getSort($data, $v['id'], $i);
            }
        }
        return $arr;
    }