Easy-to-understand PHP design pattern singleton pattern

Singleton mode ensures that a class has only one instance, instantiates itself and provides this instance to the entire system. This class is called a singleton class, Singleton modeProvides global access methods. Singleton pattern is an object creation pattern

What is the motivation for using singleton pattern?

Answer: In order to save system resources, sometimes it is necessary to ensure that there is only one instance of a certain class in the system. After this unique instance is successfully created, we cannot create another object of the same type. All Operations can only be based on this unique instance. In order to ensure the uniqueness of the object

Class diagram overview

##Code overview

final class TaskManager
{
    private static $tm = null;
    private function construct()
    {
    }
    public static function getInstance()
    {
        if (static::$tm == null) {
            static::$tm = new TaskManager();
        }
        return static::$tm;
    }
}
// final 让这个类不能被继承、让方法不能被修改 static 设置静态方法或属性的关键字

What is the role of the php design pattern factory pattern?

The difference between factory mode and singleton mode in PHP design patterns

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