PHP에서 객체의 직렬화 및 역직렬화

$num = 500;
echo serialize($num),&#39;<br>&#39;;

$name = 'peter';
echo serialize($name),&#39;<br>&#39;;

$course = ['php','mysql','thinkphp'];
echo serialize($course),&#39;<br>&#39;;

$isPass = true;
echo serialize($isPass),&#39;<br>&#39;;

class Db
{
    //连接参数与返回值
    public $db = null;
    public $host;
    private $user;
    private $pass;
    //构造方法
    public function __construct($host='localhost',$user='root',$pass='root')
    {
        //类属性初始化
        $this->host = $host;
        $this->user = $user;
        $this->pass = $pass;
        
        //创建对象时自动连接数据库
        $this->connect();
    }
    
    //连接数据库的方法
    private function connect()
    {
        $this->db = mysqli_connect($this->host,$this->user, $this->pass);
    }
    
    //serialize($obj)序列化的时候,会自动调用__sleep(void)
    //主要用于对象休眠时的一些清理工作,例如指定哪些属性允许进入到休眠对象的属性序列中
    public function __sleep()
    {
        //返回由属性名字符串组成的索引数组,指示序列化时要保存的字段名
        return ['host','user','pass'];
        //对于本案例来说,如果连接参数不变的情况下,只要将$this->db保存到对象序列中即可
//        return ['db'];
    }
    
    //unserialize()反序列化的时候,会自动调用__wakeup(void)
    //主要用于唤醒对象时要做的初始化工作,例如本例中的:自动连接数据库
    public function __wakeup()
    {
        $this->connect();
    }
    
}
$obj = new Db();

echo serialize($obj);

$tmp1 = serialize($obj);

echo $tmp1;

$tmp2 = unserialize($tmp1);

echo &#39;<hr>&#39;;
echo is_object($tmp2) ? &#39;对象&#39; : &#39;不是&#39;;
echo &#39;<hr>&#39;;

var_dump($tmp2->db);