Shulou(Shulou.com)06/03 Report--

This article mainly introduces how to realize the singleton pattern of php design pattern, which can be used for reference by interested friends. I hope you will gain a lot after reading this article.

The specific analysis is as follows:

Singleton mode (responsibility mode):

To put it simply, an object (you need to understand object-oriented ideas before learning design patterns) is only responsible for a specific task.

Singleton class:

1. The constructor needs to be marked private (access control: prevents external code from using new operators to create objects). Singleton classes cannot be instantiated in other classes, but can only be instantiated by themselves.

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

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

In addition, you need to create a _ _ clone () method to prevent objects from being copied (cloned)

Why use PHP singleton mode?

1. The application of php mainly lies in database applications, so there will be a large number of database operations in an application. Using singleton mode, a large number of resources consumed by new operations can be avoided.

2. If a class is needed in the system to control some configuration information globally, then the singleton mode can be easily implemented. You can see the FrontController section of ZF for this.

3, in a page request, easy to debug, because all the code (such as database operation class db) are concentrated in a class, we can set hooks in the class, output logs, so as to avoid everywhere var_dump, echo.

Code implementation:

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