当破坏对象相互引用时，PHP类析构函数运行缓慢

I implemented a data structure making of nodes. Each node can get its child node or parent node.

I tried to test the data structure on my web server, and found its performance is awful.

below is the sample code.

class Node
{
    public $next = null;
    public $parent = null;

    public function __construct($name) 
    {
        $this->name = $name;
    }

    public function __destruct()
    {
        static $i = 0;
        print_r(++$i.':'.$this->name.' '.date('H:i:s')."
");

        $this->next = null;
        $this->parent = null;
    }
};

$root = new Node('root');
$curNode = $root;
$count = 10;
while (--$count) {
    $curNode->next = new Node('node'.$count);
    $curNode->next->parent = $curNode;
    $curNode = $curNode->next;
}
print_r("end
");
return;

I ran it through web server and get the following result:

end
1:root 17:32:46
2:node9 17:32:46
3:node8 17:32:46
4:node7 17:32:46
5:node6 17:32:47
6:node5 17:32:47
7:node4 17:32:47
8:node3 17:32:47
9:node2 17:32:47
10:node1 17:32:48

It took almost 2 second just to destroy ten nodes. I can't find out the reason. I executed same code through cli, and it finished immediately.

My host runs Apache/2.4.29 and uses PHP 7.3.6. How can I fix it? Thank you.