PHP singleton mode example analysis, PHP singleton mode application scenarios

Examples of the singleton pattern in PHP design patterns, principles and techniques of the PHP singleton pattern, and learning how to implement the PHP singleton pattern through examples.

Single case mode (responsibility mode): An object (before learning design patterns, you need to understand object-oriented thinking) is only responsible for a specific task;

Single instance class: 1. The constructor 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 static member variable that holds an instance of the class 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)