Can php implement singleton?

php can implement a singleton. The method of implementing a singleton is: 1. Apply for a private static member variable to save the only instance of the class; 2. Declare a private constructor to prevent objects from being created outside the class. ;3. Declare a static public method for external acquisition of the only instance.

The operating environment of this article: Windows7 system, PHP7.1 version, DELL G3 computer

How to implement a singleton in PHP

• Apply for a private static member variable to save the only instance of the class

• Declare a private constructor to prevent objects from being created outside the class

• Declare a static public method for external acquisition of a unique instance

After completing these three steps, it is a singleton, but this singleton The example is not safe. If you want this singleton to be safe, you need the following two steps (please add if there are any imperfections)

• Declare a private cloning method to prevent the object from being cloned

• Override the __sleep method and leave the return blank to prevent serialization and deserialization from obtaining new objects

<?php
/**
 * 单列模式（防止对象克隆、对象序列化反序列化）
 * Created by PhpStorm.
 * User: Jeaforea
 * Date: 2019/3/14
 * Time: 17:56
 */
namespace Kanshenmekan\Buzhunkan\Zaikandasini;
class SetSingleton{
    private static $new; //申请一个私有的静态成员变量来保存该类的唯一实例
    private function __construct() {} //声明私有的构造方法，防止类外部创建对象
    public static function instance () { //声明一个静态公共方法，供外部获取唯一实例
        if (!(self::$new instanceof self)) {
            self::$new = new self;
        }
        return self::$new;
    }
    private function __clone() {} //声明私有的克隆方法，防止对象被克隆
    public function __sleep() { //重写__sleep方法，将返回置空，防止序列化反序列化获得新的对象
        return [];
    }
}

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