How to use php magic methods __get() and __set()

"__set()" is automatically called when assigning a value to an undefined attribute, the syntax is "public function __set(key,value){}"; "__get()" is called when an undefined attribute is called, Syntax "public function __get(name){}".

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

The magic method in PHP usually starts with __( It starts with two underscores) and does not need to be explicitly called but is automatically called under certain conditions.

Magic method	Function
__set()	is giving undefined Automatically called when assigning a property
__get()	Automatically called when calling an undefined property

1. __set() method

When assigning a value to a class attribute that is undefined or invisible in the current environment, the __set() method will be automatically called. The syntax format for defining this method is as follows:

public function __set($key, $value){
    ... ... ;
}

Among them, the parameter $key is the name of the variable to be operated, and $value is the value of the variable $key.

[Example] The following uses a simple example to demonstrate the use of the __set() method.

<?php
    class Website{
        public $name;
        private $url;
        public function __set($key, $value){
            echo &#39;为“&#39;.$key.&#39;”赋值“&#39;.$value.&#39;”失败！<br>&#39;;
        }
    }
    $object          = new Website();
    $object -> name  = &#39;php中文网&#39;;
    $object -> url   = &#39;https://www.php.cn/&#39;;
    $object -> title = &#39;PHP教程&#39;;
?>

The running results are as follows:

为“url”赋值“https://www.php.cn/”失败！
为“title”赋值“PHP教程”失败！

Using the characteristics of the __set() method, we can use the __set() method to assign or modify the attributes modified with the private keyword in the class. . As shown below:

<?php
    class Website{
        public $name;
        private $url = &#39;&#39;;
        public function __set($key, $value){
            if(isset($this->$key)){
                $this -> $key = $value;
            }else{
                echo &#39;为“&#39;.$key.&#39;”赋值“&#39;.$value.&#39;”失败！<br>&#39;;
            }
        }
        public function getUrl(){
            echo $this -> url;
        }
    }
    $object          = new Website();
    $object -> name  = &#39;php中文网&#39;;
    $object -> url   = &#39;https://www.php.cn/&#39;;
    $object -> title = &#39;PHP教程&#39;;
    $object -> getUrl();
?>

The running results are as follows:

为“title”赋值“PHP教程”失败！
https://www.php.cn/

2. The __get() method

is not defined or is not defined when calling or obtaining the current environment. When the class attribute is invisible, the __get() method will be automatically called. The syntax format for defining this method is as follows:

public function __get($name){
    ... ... ;
}

The parameter $name is the name of the variable to be operated.

[Example] The following uses a simple example to demonstrate the use of the __get() method.

<?php
    class Website{
        public $url = &#39;https://www.php.cn/&#39;;
        private $name = &#39;php中文网&#39;;
        public function __get($name){
            echo &#39;获取：“&#39;.$name.&#39;”失败！&#39;;
        }
    }
    $object = new Website();
    echo $object -> url.&#39;<br>&#39;;
    echo $object -> name.&#39;<br>&#39;;
    echo $object -> title.&#39;<br>&#39;;
?>

The running results are as follows:

https://www.php.cn/
获取：“name”失败！
获取：“title”失败！

Recommended learning: "PHP Video Tutorial"

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