An in-depth explanation of the principles of PHP plug-in mechanism_PHP tutorial

In this article we mainly tell you some

Plug-in, also known as Plug-in, refers to a specific type of functional module (usually composed of Implemented by third-party developers), its characteristics are: activate it when you need it, disable/delete it when you don’t need it; and whether it is activated or disabled, it does not affect the operation of the core module of the system, which means that the plug-in is A non-intrusive modular design achieves loose coupling of core programs and plug-in programs. 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 PHP plug-in mechanism, I think, must have the following features:

Dynamic monitoring and loading of plug-ins (Lookup)

Dynamic triggering of plug-ins

The implementation of the PHP plug-in mechanism in the above two points does not affect the operation of the core program

To implement plug-ins in the program, the first thing we should think of is to define different hooks (Hooks); "Hook" is a very vivid image The logical concept is that 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, such as the hook I mentioned earlier about comment spam filtering. Usually it has been designed by the core system developers into the comment processing logic; another category Hooks may be customized by users (developed by third-party developers) and usually exist in the presentation layer, such as an ordinary PHP form display page.

Maybe you find the above words boring and drowsy; but to understand the code I wrote below, it is essential to understand the principles of the above PHP plug-in mechanism.

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:

is responsible for monitoring all registered plug-ins and instantiating these plug-in objects.

is 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 the following display code See this rule.

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

I talked a lot about the principles of PHP plug-in mechanism. Let’s take a look at my implementation plan:

Plugin Manager PluginManager class:

The following is PHP Content cited by the plug-in mechanism:

1. < ?
2. class PluginManager
3. {
4. private $_listeners = array();
5. public function __construct()
6. {
7. #Here the $plugin array contains the plug-in information we obtain that has been activated by user
   
8. #For the convenience of demonstration, we assume $plugin Contains at least
9. #$plugin = array (
10. # 'name' => 'Plugin name',
11. # 'directory'=>'plugin Installation directory'
12. #);
13. $plugins = get_active_plugins();
    # Please implement this function yourself
14. if($plugins)
15. {
16. foreach($plugins as $plugin)
17. {//Assume that each The plug-in folder contains an actions.
    php file, which is the specific implementation of the plug-in
18. if (@file_exists(STPATH ​​.'plugins/'.
    $plugin[ 'directory'].'/actions.php'))
19. {
20. include_once(STPATH ​​.'plugins/'.
    $plugin['directory'].'/actions.php');
21. $class = $ plugin['name'].'_actions';
22. if (class_exists($class))
23. {
24. //Initialize all plug-ins
25. new $class($this);
26. }
27. }
28. }
29. }
30. #Do something here Logging stuff
31. }
32. function register($hook, &$reference,
    $method)
33. {
34. //Get the method to be implemented by the plug-in
35. $key = get_class($reference).'- >'.$method;
36. //Push the plug-in reference and the method into the listening array
37. $this->_listeners[$hook][$key] =
    array( &$reference, $method);
38. # Do some logging stuff here
39. }
40. function trigger($hook, $data='')
41. {
42. $result = '';
43. //Check whether the hook to be implemented is in the listening array
44. if (isset($this->_listeners[$hook])
    && is_array($this->_listeners[$hook])
    && count($this->_listeners[$hook]) > 0)
45. {
46. // Loop call starts
47. foreach ($this->_listeners[$hook] as $listener)
48. {
49. // Get the reference and method of the plug-in object
50. $class =& $listener[0];
51. $method = $listener[1];
52. if(method_exists($class,$method))
53. {
54. // Method of dynamically calling plug-ins
55. $result .= $class->$method($data);
56. }
57. }
58. }
59. #Do some logging stuff here
60. return $ result;
61. }
62. }
63. ?>

Add the above code The core of the entire plug-in mechanism is completed with no more than 100 lines of comments. It should be noted again that you must set it as a global class and load it first wherever the plug-in is needed. The places commented with # are the parts you need to complete yourself, including the acquisition and logging of the PHP plug-in mechanism, etc.