Usage analysis of __get() and __set in PHP

In PHP5, we are provided with special methods for setting and obtaining values ​​for attributes, the two methods "__set()" and "__get()". These two methods do not exist by default, but we manually Added to the class, like the constructor method (__construct()), it will only exist if it is added to the class. You can add these two methods in the following way. Of course, you can also add them according to your personal style:

//__set()方法用来设置私有属性
    public function __set($name,$value){       
     $this->$name = $value;    }   
      //__get()方法用来获取私有属性   
       public function __get($name)
       {        return $this->$name;    }

__get() method: This method is used to get the private member attribute value. It has one parameter. The parameter is passed in the name of the member attribute you want to get, and the obtained attribute value is returned. This method does not require us to do it manually. to call, because we can also make this method a private method, which is automatically called by the object when the private property is directly obtained. Because the private property has been encapsulated, the value cannot be obtained directly. However, if you add this method to the class, you will automatically obtain the value directly when using a statement such as "echo$p1->name". Call the __get($name) method and pass the attribute name to the parameter $name. Through the internal execution of this method, the value of the private attribute we passed in is returned. If the member properties are not encapsulated as private, the object itself will not automatically call this method.

__set() method: This method is used to set values ​​for private member attributes. It has two parameters. The first parameter is the name of the attribute you want to set the value for, and the second parameter is The value to be set for the property. There is no return value. This method also does not need to be called manually. It can also be made private. It is automatically called when directly setting the private attribute value. The same private attribute has been encapsulated with

. If there is no __set () This method is not allowed, for example: $this->name='zhangsan', this will cause an error, but if you add the __set($property_name, $value) method to the class, you can directly When assigning a value to a private attribute, it will be automatically called, passing the attribute such as name to $property_name, and passing the value "zhangsan" to be assigned to $value. Through the execution of this method, the purpose of assignment is achieved. If the member properties are not encapsulated as private, the object itself will not automatically call this method. In order not to pass in illegal values, you can also make a judgment in this method. The code is as follows:

<?php
class Person
{
//下面是人的成员属性，都是封装的私有成员
private $name;      //人的名子
private $sex;       //人的性别
private $age;       //人的年龄
//__get()方法用来获取私有属性
private function __get($property_name)
{
echo "在直接获取私有属性值的时候，自动调用了这个__get()方法<br>";
if(isset($this->$property_name))
{
return($this->$property_name);
}
else
{
return(NULL);
}
}
//__set()方法用来设置私有属性
private function __set($property_name, $value)
{
echo "在直接设置私有属性值的时候，自动调用了这个__set()方法为私有属性赋值<br>";
$this->$property_name = $value;
}
}
$p1=newPerson();
//直接为私有属性赋值的操作，会自动调用__set()方法进行赋值
$p1->name="张三";
$p1->sex="男";
$p1->age=20;
//直接获取私有属性的值，会自动调用__get()方法，返回成员属性的值
echo "姓名：".$p1->name."<br>";
echo "性别：".$p1->sex."<br>";
echo "年龄：".$p1->age."<br>";
?>
程序

Execution result:

When directly setting the private attribute value, the __set() method is automatically called to assign the private attribute value
When directly setting the value When the private attribute value is set, the __set() method is automatically called to assign the private attribute value.
When the private attribute value is directly set, the __set() method is automatically called to assign the private attribute value.
After direct acquisition When the private attribute value is obtained, the __get() method is automatically called
Name: Zhang San
When the private attribute value is directly obtained, the __get() method is automatically called
Gender: Male
When directly obtaining the private attribute value, the __get() method is automatically called
Age: 20

If the above code does not add the __get() and __set() methods, the program An error will occur because private members cannot be operated outside the class, and the above code helps us directly access the encapsulated private members by automatically calling the __get() and __set() methods.

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