What are the simple interest design patterns in PHP?

php single-interest design patterns include: 1. Hungry-style singleton mode, which means to create an instance when the class is loaded and then directly return the instance; 2. Lazy-style singleton mode, in the first time An instance is created only when the method to obtain the instance is called to achieve delayed loading; 3. Double check locking singleton mode, based on the lazy singleton mode, ensures thread safety through locking, achieving delayed loading and thread safety; 4. Use the singleton mode of static variables, save the instance in the static variable, and provide a static method to obtain the instance to achieve simple thread safety.

The operating environment of this article: Windows 10 system, PHP8.1.3 version, Dell G3 computer.

PHP singleton design pattern is a commonly used design pattern, which is used to ensure that a class has only one instance and provides a global access point.

In PHP, there are several ways to implement the singleton design pattern:

Hungry Chinese Singleton Pattern

Hungry Chinese Singleton The pattern means to create an instance when the class is loaded and then return the instance directly. The advantage of this method is that it is simple to implement and thread-safe, but the disadvantage is that lazy loading cannot be achieved.

class Singleton {
    private static $instance = new Singleton();
    private function __construct() {}
    public static function getInstance() {
        return self::$instance;
    }
}

Lazy singleton mode

Lazy singleton mode means that an instance is created only when the method to obtain the instance is called for the first time. The advantage of this approach is that it can implement lazy loading, but the disadvantage is that thread safety issues may occur in a multi-threaded environment.

class Singleton {
    private static $instance = null;
    private function __construct() {}
    public static function getInstance() {
        if (self::$instance == null) {
            self::$instance = new Singleton();
        }
        return self::$instance;
    }
}

Double check locking singleton mode

Double check locking singleton mode is based on the lazy singleton mode and ensures thread safety through locking. The advantage of this approach is that it achieves lazy loading and thread safety, but the disadvantage is that it increases code complexity.

class Singleton {
    private static $instance = null;
    private function __construct() {}
    public static function getInstance() {
        if (self::$instance == null) {
            synchronized(self::class) {
                if (self::$instance == null) {
                    self::$instance = new Singleton();
                }
            }
        }
        return self::$instance;
    }
}

The singleton mode using static variables

The singleton mode using static variables means saving the instance in a static variable and providing a static method to obtain it. this instance. The advantage of this method is that it is simple to implement and thread-safe, but the disadvantage is that lazy loading cannot be achieved.

class Singleton {
    private static $instance = null;
    private function __construct() {}
    public static function getInstance() {
        if (self::$instance == null) {
            self::$instance = new Singleton();
        }
        return self::$instance;
    }
}

The above are the implementation methods of several common PHP singleton design patterns. Depending on the specific needs and scenarios, you can choose the appropriate way to implement the singleton.

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