Usage of __get() and __set in PHP_PHP Tutorial

PHP object-oriented _get(), _set() usage

Generally speaking, always define class attributes 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.
PHP5 provides us 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. It goes inside, like the constructor method (__construct()), it will only exist if it is added inside 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() method is used to set private properties
Public function __set($name,$value){
$this->$name = $value;
}
 
//__get() method is used to obtain private attributes
Public function __get($name){
           return $this->$name;
}

__get() method: This method is used to get the private member attribute value. It has a 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 need to be called manually, because we also This method can be made into a private method, which is automatically called by the object when private properties are 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 value you want to set for the attribute. 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
{
//The following are the member attributes of people, which are all encapsulated private members
private $name; //The person’s name
private $sex; //Person’s gender
private $age; //The person’s age
//__get() method is used to obtain private attributes
private function __get($property_name)
{
echo "When directly obtaining the private attribute value, this __get() method is automatically called
";
if(isset($this->$property_name))
{
return($this->$property_name);
}
else
{
return(NULL);
}
}
//__set() method is used to set private attributes
private function __set($property_name, $value)
{
echo "When directly setting the value of a private attribute, the __set() method is automatically called to assign a value to the private attribute
";
$this->$property_name = $value;
}
}
$p1=newPerson();
//The operation of directly assigning values ​​​​to private attributes will automatically call the __set() method to assign values ​​
$p1->name="Zhang San";
$p1->sex="Male";
$p1->age=20;
//Get the value of the private attribute directly, the __get() method will be automatically called, and the value of the member attribute will be returned
echo "Name:".$p1->name."
";
echo "Gender:".$p1->sex."
";
echo "Age:".$p1->age."
";
?>
Program execution result:
When directly setting the value of a private attribute, the __set() method is automatically called to assign a value to the private attribute
When directly setting the value of a private attribute, the __set() method is automatically called to assign a value to the private attribute
When directly setting the value of a private attribute, the __set() method is automatically called to assign a value to the private attribute
When directly obtaining the private attribute value, the __get() method is automatically called
Name: Zhang San
When directly obtaining the private attribute value, 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 will go wrong, because private members cannot be operated outside the class, and the above code automatically calls the __get() and __set() methods. To help us directly access the encapsulated private members.