Revealing the secrets of PHP permission control modifiers: Mastering the usage skills in practical applications

PHP is a programming language widely used in web development. When developing web applications, permission control is an essential part. Permission control can ensure the data security and functional integrity of the application. PHP provides many permission control modifiers, which this article will discuss.

Introduction to permission control modifiers

In PHP, there are three main types of permission control modifiers: public, protected, and private.

Public means public access, and its properties and methods can be accessed anywhere inside and outside the class.

protected means protected access, and its properties and methods can be accessed in the current class and subclasses.

private means private access, and its properties and methods can only be accessed in the current class.

In addition to the above three permission control modifiers, there are also final and static.

final represents the final class, and its properties and methods cannot be inherited.

static represents a static class. Its properties and methods can be accessed anywhere inside and outside the class, and can be used without instantiating the class.

The principle of implementing permission control

The properties and methods in the class have a modifier to limit their visibility, thereby achieving permission control.

The PHP parser will determine access permissions based on modifiers. If a property or method does not define a modifier, it defaults to public.

Usage skills in practical applications

Now we will master the use skills of permission control modifiers through actual application scenarios.

1. Prevent attributes from being tampered

In many web applications, in order to ensure the integrity and security of data, we need to restrict some attributes to prevent them from being tampered with. This can be achieved using the private attribute modifier.

The following is an example:

class User {
    private $username;
    private $password;
    
    public function __construct($username, $password) {
        $this->username = $username;
        $this->password = $password;
    }
    
    public function getUsername() {
        return $this->username;
    }
    
    public function getPassword() {
        return $this->password;
    }
}

$user = new User('Tom', '123456');
$user->username = 'Jerry'; // 禁止修改

2. Prevent methods from being overridden

In some cases, we hope that a method of a class cannot be overridden Overriding by its subclasses can be achieved using the final attribute modifier.

The following is an example:

class Animal {
    final public function move() {
        echo 'Moving...';
    }
}
 
class Dog extends Animal {
    // 错误示例
    public function move() {
        echo 'Running...';
    }
}

$dog = new Dog();
$dog->move(); // 输出 Moving...

3. Protect attribute access

When you need to restrict access to certain attributes, you can use the protected attribute modifier .

The following is an example:

class Person {
    protected $name;
    
    public function __construct($name) {
        $this->name = $name;
    }
}

class Student extends Person {
    public function getName() {
        // 错误示例
        return $this->name;
    }
}

$student = new Student('Tom');
echo $student->getName(); // 输出空白，无法访问父类属性

4. Implementing controlled access

In complex applications, some properties or methods need to be updated For fine-grained access control, public methods can be used to get or set property values. This allows you to control property access via public methods.

The following is an example:

class User {
    private $username;
    private $password;
    
    public function __construct($username, $password) {
        $this->username = $username;
        $this->password = $password;
    }
    
    public function setUsername($username) {
        // 禁止修改用户名
        if ($this->username === $username) {
            return false;
        }
        
        $this->username = $username;
        return true;
    }
    
    public function setPassword($password) {
        $this->password = $password;
    }
    
    public function getUsername() {
        return $this->username;
    }
    
    public function getPassword() {
        return $this->password;
    }
}

$user = new User('Tom', '123456');
$user->setUsername('Jerry'); // 禁止修改
$user->setPassword('654321');
echo $user->getUsername() . ':' . $user->getPassword(); // 输出 Tom:654321

Summary

In PHP development, permission control is a very important part. Through permission control, you can control the access scope and protect data security. , improve the reliability and stability of applications. This article introduces the commonly used permission control modifiers in PHP, and explains and demonstrates them through actual application scenarios. I hope it will be helpful to PHP developers.

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