Introduction to the method of implementing plug-in mechanism in php

The content introduced in this article is my understanding of the plug-in mechanism and its implementation in PHP. This solution is only one of the implementation methods of the plug-in mechanism and is for reference only.

The content introduced in this article is my understanding of the plug-in mechanism and its implementation in PHP. This solution is only one of the implementation methods of the plug-in mechanism and is for reference only.

Plug-in, also known as Plug-in, refers to a specific type of functional module (usually implemented by third-party developers). Its characteristics are: activate it when you need it, and disable/delete it when you don’t need it. ; And whether it is activated or disabled, it will not affect the operation of the core module of the system. In other words, the plug-in is a non-intrusive modular design that achieves loose coupling between the core program and the plug-in program. A typical example is the numerous third-party plug-ins in WordPress, such as the Akimet plug-in, which is used to filter spam on user comments.

A robust plug-in mechanism, I think, must have the following characteristics:

Dynamic monitoring and loading of plug-ins (Lookup) Dynamic triggering of plug-ins

The implementation of the above two points will not affect the operation of the core program

To implement plug-ins in a program, the first thing we should think of is to define different hooks; "hook" is a very vivid logical concept, and you can think of it as a plug-in trigger condition reserved by the system. Its logic principle is as follows: when the system executes a certain hook, it will determine whether the conditions of the hook are met; if it is met, it will first call the function specified by the hook, and then return to continue executing the rest of the program; if it is not met, it will first call the function specified by the hook. , just skip it. This is a bit like "interrupt protection" logic in assembly.

Some hooks may have been designed by the system in advance. For example, the hook I mentioned earlier about comment spam filtering has usually been designed by the core system developers into the comment processing logic; another type of hook may be designed by User-customized (formulated by third-party developers), usually exists in the presentation layer, such as an ordinary PHP form display page. Please pay attention to understand the following instructions.

The following is the core implementation of the plug-in mechanism in PHP. The core of the entire mechanism is divided into three major blocks:

A plug-in manager class: This is the core of the core. It is an application global Global object. It has three main responsibilities:

Responsible for monitoring all registered plug-ins and instantiating these plug-in objects. Responsible for registering all plugins. When the hook condition is met, the corresponding object method is triggered.

Plug-in function implementation: This is mostly done by third-party developers, but certain rules need to be followed. This rule is stipulated by the plug-in mechanism and varies depending on the plug-in mechanism. You will see this rule in the display code below.

Plug-in triggering: That is, the triggering condition of the hook. Specifically, this is a small piece of code, placed where you need the plug-in implementation, to trigger this hook.