thinkphp5中__destruct何时执行？

namespace app\shop\drive;

class Redis {

    public $handler;

    public function __construct(){

        $redis = new \Redis();

        $redisCOnf= config('cache.redis');

        $redis->connect($redisConf['host'], $redisConf['port']);

        $redis->auth($redisConf['password']);

        $this->handler = $redis;

    }



    public function __destruct(){

        $this->handler->close();

    }

}

    ...

    public $redis, $prefix;

    protected function _initialize(){

        $this->initRedis();

        var_dump($this->redis->info()); //出错，redis连接已关闭

    ｝

    private function initRedis()

    {

        $redis = new Redis;

        $this->redis = $redis->handler;

        var_dump($this->redis->info()); //正常

        $this->prefix = config('cache.redis')['prefix'];

    }