PHP singleton mode (responsibility mode)

Simply put, an object (before learning design patterns, you need to understand object-oriented thinking) is only responsible for a specific task;

Single instance class:

1. Constructor It needs to be marked as private (access control: to prevent external code from using the new operator to create objects). The singleton class cannot be instantiated in other classes and can only be instantiated by itself;

2. Have a saved class Static member variables of the instance

3. Have a public static method to access this instance (the getInstance() method is commonly used to instantiate a singleton class, and the instanceof operator can be used to detect whether the class has been instantiated. )

In addition, you need to create a __clone() method to prevent the object from being copied (cloned)

<?php
/**
 * Created by PhpStorm.
 * User:
 * Date: 2017/1/2
 * Time: 下午3:32
 */

class Single {
    //保存实例的私有静态实例变量
    private static $instance;

    //private标记的构造方法，方式通过其他方式实例化
    private function __construct() {
        echo "this is construct function";
    }

    //创建clone方法防止被克隆
    public function __clone() {
        trigger_error("Clone is not allowed ", E_USER_ERROR);
    }

    //单例方法，用户访问实例的公共静态方法
    public static function shareInstance() {
        //instanceof：判断instance是不是self的实例或者子类
        if (!(self::$instance instanceof self)){
            self::$instance = new self();
        }
        return self::$instance;
    }
}

Attachment

trigger_error() Function creates user-level error messages.

trigger_error() The function can be associated with the built-in error handler, or a user-defined function can be used as a new error handler (set_error_handler()).

trigger_error(errormsg,errortype);

Parameters	Description
errormsg	Required. Specifies the error message. Maximum length 1024 bytes.
errortype	Optional. Specifies the error type. Possible values: E_USER_ERRORE_USER_WARNINGE_USER_NOTICE (default)

## Simply put, an object (before learning design patterns, you need to know more about object-oriented Thought) is only responsible for a specific task;

Singleton class:

1. The constructor needs to be marked as private (access control: prevent external code from using the new operator to create objects), singleton A class cannot be instantiated in other classes, but can only be instantiated by itself;

2. Have a static member variable that saves an instance of the class

3. Have a public member variable that accesses this instance Static method (the getInstance() method is commonly used to instantiate a singleton class, and the instanceof operator can be used to detect whether the class has been instantiated)

In addition, you need to create a __clone() method to prevent the object from being copied ( Clone)

<?php
/**
 * Created by PhpStorm.
 * User:
 * Date: 2017/1/2
 * Time: 下午3:32
 */

class Single {
    //保存实例的私有静态实例变量
    private static $instance;

    //private标记的构造方法，方式通过其他方式实例化
    private function __construct() {
        echo "this is construct function";
    }

    //创建clone方法防止被克隆
    public function __clone() {
        trigger_error("Clone is not allowed ", E_USER_ERROR);
    }

    //单例方法，用户访问实例的公共静态方法
    public static function shareInstance() {
        //instanceof：判断instance是不是self的实例或者子类
        if (!(self::$instance instanceof self)){
            self::$instance = new self();
        }
        return self::$instance;
    }
}

Attached

trigger_error() Function creates a user-level error message.

trigger_error() The function can be associated with the built-in error handler, or a user-defined function can be used as a new error handler (set_error_handler()).

trigger_error(errormsg,errortype);

ParametersDescriptionRequired. Specifies the error message. Maximum length 1024 bytes. Optional. Specifies the error type. Possible values: E_USER_ERRORE_USER_WARNINGE_USER_NOTICE (default)

errormsg
errortype

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