SPL--Serializable

Serializable[自定义序列化的接口] ：

实现此接口的类将不再支持 __sleep() 和 __wakeup()。

作用：

为一些高级的序列化场景提供支持。__sleep()和__wakeup()有一些问题，这些问题再SPL中都得到解决。【书上说的，具体的问题之看到了“总结”中的第一个】

总结：（根据看到的例子总结，绝对地不全）

1.魔术方法不能序列化基类的私有变量，SPL可以。

2.SPL可通过子类serialized父类。

3.SPL可以serialize全部的子类变量，子类不需要重写serialize方法。

4.在serialize方法中return NULL 来防止序列化。

以例服人：

1.魔术方法不能序列化基类私有变量

<?php

error_reporting( E_ALL );  //开启全部错误提示

class Base {
    private $base;

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

class Sub extends Base{
    private $sub;

    public function __construct() {
        parent::__construct();  //调用父类的构造方法，为父类中的base赋值
        $this->sub = "sub";
    }

    public function __sleep() {
        return array( "sub", "base" );
    }
}

$instance = new Sub();
$serialized = serialize( $instance );
echo $serialized."
";
$restored = unserialize( $serialized );

//执行输出
//Notice: serialize(): "base" returned as member variable from __sleep() but does not exist
//O:3:"Sub":2:{s:8:"NULSubNULsub";s:3:"sub";s:4:"base";N;}

使用SPL的Serializable接口就可以解决这个问题

<?php

error_reporting( E_ALL );  //开启全部错误提示

class Base implements Serializable {
    private $base;

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

    public function serialize() {
        return serialize( $this->base );
    }

    public function unserialize( $serialized ) {
        $this->base = unserialize( $serialized );
    }

    public function getBase() {
        return $this->base;
    }
}

class Sub extends Base{
    private $sub;

    public function __construct() {
        parent::__construct();  //调用父类的__construct,为父类的base赋值，可通过调用父类的getBase方法获取改值。
        $this->sub = "sub";
    }

    public function serialize() {
        $baseSerialized = parent::serialize();  //注意这个地方
        return serialize( array( $this->sub, $baseSerialized ) );
    }

    public function unserialize( $serialized ) {
        $temp = unserialize( $serialized );
        $this->sub = $temp[0];
        parent::unserialize( $temp[1] );
    }
}

$instance = new Sub();
$serialized = serialize( $instance );
echo $serialized."
";
$restored = unserialize( $serialized );
echo $restored->getBase();

//执行输出
//C:3:"Sub":43:{a:2:{i:0;s:3:"sub";i:1;s:11:"s:4:"base";";}}
//base

2.通过子类序列化父类

<?php

class Base implements Serializable{
    private $data;

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

    public function getData() {
        return $this->data;
    }

    public function serialize() {
        return serialize( $this->data );
    }

    public function unserialize( $serialize ) {
        $this->data = unserialize( $serialize );
    }
}

class Sub extends Base{
    private $id;
    private $name;

    public function __construct( $id, $name, $data ) {
        parent::__construct( $data );
        $this->id = $id;
        $this->name = $name;
    }

    public function serialize() {
        return serialize(
            array(
                "id" => $this->id,
                "name" => $this->name,
                "parentData" => parent::serialize()  //注意这里
            )
        );
    }

    public function unserialize( $serialize ) {
        $temp = unserialize( $serialize );
        $this->id = $temp["id"];
        $this->name = $temp["name"];
        parent::unserialize( $temp["parentData"] );
    }

    public function getVar() {
        return $this->id."|".$this->name."|".parent::getData();
    }
}

$instance = new Sub( 12, "lee", "hello world" );
$serialized = serialize( $instance );
echo $serialized."
";
$unserialized = unserialize( $serialized );
echo $unserialized->getVar();

//echo
//C:3:"Sub":86:{a:3:{s:2:"id";i:12;s:4:"name";s:3:"lee";s:10:"parentData";s:19:"s:11:"hello world";";}}
//12|lee|hello world

3.子类不用重写父类serialize方法也能序列化自身的变量，用get_object_vars()函数配合。

<?php

class Pot implements Serializable
{
    protected $_a;
    protected $_b;

    public function serialize() {
        return serialize( get_object_vars( $this ) );
    }
    public function unserialize( $data ) {
        $values = unserialize( $data );
        foreach ( $values as $key=>$value ) {
            $this->$key = $value;
        }
    }
}

//And now one descendant:

class PotId extends Pot
{
    protected $_k;
}

class Pots extends PotId
{
    protected $_l;
}

$pots = new Pots();

echo serialize( $pots );

//echo
//C:4:"Pots":50:{a:4:{s:2:"_l";N;s:2:"_k";N;s:2:"_a";N;s:2:"_b";N;}}

4.为了防止通过unserialize得到对象，可以在serialize方法中return NULL,这将放回一种序列化后的NULL。

<?php

class testNull implements Serializable{
    public function serialize() {
        return NULL;
    }
    public function unserialize($serialized) {

    }
}

$instance = new testNull();
$serialized = serialize($instance);
echo $serialized;  //N;