The basis for implementing AOP in PHP

This article mainly introduces the basics of implementing AOP in PHP. It has a certain reference value. Now I share it with everyone. Friends in need can refer to it

AOP is the continuation of OOP and is Aspect Oriented Programming The abbreviation of means aspect-oriented programming, and some also call it aspect-oriented programming. Aspect-oriented programming is useful in enterprise-level development. For example, before we call certain methods, we need to make a log record, and after calling the method, we also need a log record. Let’s first look at how we can implement it in PHP without using AOP.

<?php
/**
 * 日志类 
 */
 class SystemLog {    
 function beforeLog() {        
 // write before log    
 }    
    function afterLog() {       
     // write after log    
     }
} 
/**
 * 新闻类 
 */
 class News extends SystemLog {    
 function add() {        
 $this->beforeLog();        
 // add news
        $this->afterLog();
    } 
    function delete() {        
    // delete news   
     }
}

We define a log class, which contains two methods beforeLog() and afterLog(), which are used to record logs before and after calling the method. , then we defined the news class, which inherits the log class. To complete logging before and after calling the add() method, we only need to call the beforeLog() and afterLog() methods inside the add() method. Although we implement logging before/after calling the add() method, such code is not elegant at all in OOP programming, and it also violates the idea of ​​"weak coupling, strong cohesion", because add( under the News class ) method should only do the one thing of adding news, and then we record the log in the add() method. In addition, if we need to add logging functions to many methods, then beforeLog() and afterLog() will be called many times. ) method, which brings a lot of duplicate code.

In PHP5, if an undefined method is called, the _call() method will be automatically called. Taking advantage of this feature of PHP5, we can implement AOP programming in the _call() method. This kind of AOP programming is just a prototype of AOP and is not as powerful as Java.

<?php
/**
 * 日志类 
 */
 class SystemLog {    
 function _call($method,$args) {        
 $method = "_$method"; // 在要调用的方法名前加‘_’，$method为要调用的方法名
        // write before log
        $return = call_user_func_array(array($this, $method), $args);        
        // write after log 
        return $return;
    } 
} 
/**
 * 新闻类 
 */
 class News extends SystemLog {    
 function _add() {        
 // add news    
 } 
    function delete() {        
    // delete news    
    }
}

The news class still inherits the log class. It should be noted that we added '_' before the add() method, which does not Any logging related code.

$news = new News();
$news->add();

Call the add() method in the News class. Note that there is no add() method in the rewritten News class, only the _add() method. , when PHP cannot find the add() method, it will automatically call the _call() method. The _call() method has two parameters. The first parameter is the name of the called method, and the second parameter is the name of the called method. Parameters, in the _call() method, first add '_' before the called method name. Here, after adding '_', the method becomes _add. The _add() method exists in the News class. Then write the pre-method call log, and then use the call_user_func_array() function to execute the pre-object method call. After the method call is completed, write the post-method call log.

To review, we used programming conventions and the feature of PHP5 that calling an undefined method will automatically call the _call() method to implement AOP, but the AOP here is only a prototype, and the function is not powerful enough. With the development of PHP, I believe that PHP will be more powerful in AOP in the future.

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