What is the difference between get and set in php

The difference between get and set in php: The "__get()" method is used to obtain the attribute value of a private member. The returned result is the obtained attribute value, while the "__set()" method is used to obtain the attribute value of a private member. When setting the value of a private member attribute, this method has no return value.

The operating environment of this tutorial: windows10 system, PHP7.1 version, DELL G3 computer

What is the difference between get and set in php

Generally speaking, always define the attributes of a class as private, which is more in line with realistic logic. However, reading and assigning operations to attributes are very frequent, so in PHP5, two functions "__get()" and "__set()" are predefined to obtain and assign attributes. It is similar to the operation of javabean in java, and the method used is similar, except that there is no need to perform set and get operations on each field like in javabean. Just add two magic methods. That is, the operations of setting and obtaining values ​​of private members.

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 add them to the class manually. 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 value of a private member attribute. 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. , we don’t need to call this method manually, because we can also make this method a private method, which is automatically called by the object when the private attribute 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. The second parameter is the name of the attribute you want to set the value for. The first parameter is the value to be set for the attribute, and 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

, if there is no __set() method, it is not allowed, for example: $this->name='zhangsan', this will cause an error, but if you add __set($property_name, $value) to the class ) This method will be automatically called when directly assigning a value to a private attribute. Pass the attribute such as name to $property_name, and pass the value "zhangsan" to be assigned to $value. Through the execution of this method, the assignment is achieved. Purpose. 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:

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
     public 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
     public 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 = new Person();
 //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>";

Program execution result:

When directly setting the value of a private property, the __set() method is automatically called to assign a value to the private property

When directly setting the value of a private property When setting the value of a private attribute, the __set() method is automatically called to assign a value to the private attribute

When the value of a private attribute is set directly, the __set() method is automatically called to assign a value to the private attribute

When directly obtaining the private attribute value, this __get() method is automatically called

Name: Zhang San

When directly obtaining the private attribute value, the __get() method is automatically called This __get() method

Gender: Male

When directly obtaining the private attribute value, this __get() method is automatically called

Age: 20

If the above code does not add the __get() and __set() methods, the program will go wrong, because private members cannot be operated outside the class, and the above code automatically calls __get() and _ The _set() method helps us directly access the encapsulated private members.

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