Detailed explanation of __set and __get methods in PHP and their application scenarios

In PHP, there are two very useful magic methods (__set and __get), which are used to control the reading and writing operations of member attributes. This article will delve into the use of these two magic methods and their application scenarios in PHP.

__set method

When we assign a value to a property that does not exist or is inaccessible, PHP will automatically call the __set method. For example:

class Person {
    private $name;

    public function __set($key, $value) {
        if ($key == 'name') {
            $this->name = $value;
        }
    }
}

$person = new Person();
$person->name = 'Lucas';

In the above example, we created a class Person and defined a private property $name in the class. We also define a __set method, which will determine which attribute value to set based on the $key passed in. If $key equals 'name', the passed in value is assigned to the $name attribute.

We create a $person object and set the value of the name attribute to it. Since this property is private, we cannot access it directly. However, if we assign a value to it through $person->name, the __set method will actually be called automatically.

__get method

Compared with the __set method, the __get method is more commonly used. When we try to read the value of a property that does not exist or is inaccessible, PHP automatically calls the __get method. For example:

class Person {
    private $name;

    public function __get($key) {
        if ($key == 'name') {
            return $this->name;
        }
    }
}

$person = new Person();
echo $person->name;

In the above example, we defined a __get method, which will determine which attribute value to obtain based on the $key passed in. If $key equals 'name', returns the value of the $name attribute.

We create a $person object and try to read the value of its name attribute. Since this property is private, we cannot access it directly. However, if we obtain its value through $person->name, the __get method will actually be called automatically.

Application Scenario

The __set and __get methods can be used to control the reading and writing operations of member attributes. This is very useful in code, especially in code that requires access control and data validation of private properties.

The following is a simple class named User that uses the __set and __get methods to control the read and write operations of the user's name and age attributes:

class User {
    private $name;
    private $age;

    public function __set($key, $value) {
        switch ($key) {
            case 'name':
                $this->setName($value);
                break;
            case 'age':
                $this->setAge($value);
                break;
        }
    }

    public function __get($key) {
        switch ($key) {
            case 'name':
                return $this->name;
                break;
            case 'age':
                return $this->age;
                break;
        }
    }

    private function setName($name) {
        if (!is_string($name)) {
            throw new InvalidArgumentException('name must be a string');
        }

        $this->name = $name;
    }

    private function setAge($age) {
        if (!is_int($age)) {
            throw new InvalidArgumentException('age must be an integer');
        }

        $this->age = $age;
    }
}

$user = new User();
$user->name = 'Lucas';
$user->age = 26;

echo $user->name;
echo $user->age;

In the above example, We created a User class and implemented __set and __get methods in them. We also define a private method setName and setAge to check the validity of the name and age attributes entered by the user.

When we assign values ​​to the name and age attributes, the __set method will be automatically called. In the __set method, we delegate the assignment operation to the setName or setAge method based on the value of $key.

When we try to read the name and age attributes, the __get method is automatically called. In the __get method, we obtain the corresponding attribute value based on the value of $key.

Summary

The __set and __get methods are two very useful magic methods in the PHP language. They can be used to control the reading and writing of member properties, especially in code that requires access control and data validation of private properties. We have mastered the basic usage and application scenarios of these two methods through some sample codes, hoping to be helpful to readers.

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