What are the permission control modifiers in PHP?

Permission control modifiers in PHP include public modifier, protected modifier and private modifier. Detailed introduction: 1. The public modifier is the most commonly used permission control modifier. It means public, that is, the property or method can be accessed anywhere. Properties and methods modified with the public modifier can be accessed both inside and outside the class. Access; 2. The protected modifier indicates that it is protected, that is, the attribute or method can only be accessed in the current class and subclasses, and is not accessible externally, etc.

The operating system of this tutorial: Windows10 system, PHP version 8.1.3, DELL G3 computer.

In PHP, permission control modifiers are used to restrict access to properties and methods of a class. PHP provides three permission control modifiers, namely public, protected and private. The usage and characteristics of these three permission control modifiers will be introduced in detail below.

1. Public modifier:

The public modifier is the most commonly used permission control modifier. It means that it is public, that is, the property or method can be accessed from anywhere. Properties and methods modified with the public modifier can be accessed both inside and outside the class. For example:

class MyClass {
    public $publicProperty;
    
    public function publicMethod() {
        // 公共方法的实现
    }
}

In the above example, $publicProperty is a public property that can be accessed and modified both inside and outside the class. publicMethod() is a public method that can be called both inside and outside the class.

2. protected modifier:

The protected modifier indicates that it is protected, that is, the property or method can only be accessed in the current class and subclasses, and is not accessible externally. Properties and methods modified with the protected modifier can be accessed within the class and in subclasses. For example:

class MyClass {
    protected $protectedProperty;
    
    protected function protectedMethod() {
        // 受保护方法的实现
    }
}

In the above example, $protectedProperty is a protected property that can only be accessed and modified in the current class and subclasses. protectedMethod() is a protected method that can only be called in the current class and subclasses.

3. Private modifier:

The private modifier means private, that is, the property or method can only be accessed in the current class, and is not accessible to subclasses and outside. Properties and methods modified with the private modifier can only be accessed within the class. For example:

class MyClass {
    private $privateProperty;
    
    private function privateMethod() {
        // 私有方法的实现
    }
}

In the above example, $privateProperty is a private property that can only be accessed and modified in the current class. privateMethod() is a private method that can only be called in the current class.

It should be noted that permission control modifiers can only be used for class attributes and methods, not constants. In addition, the permission control modifier can only limit the external visibility of the class, but there is no restriction on the internal access of the class. Even privately modified properties and methods can still be accessed and called within the class.

The selection of permission control modifiers should be determined based on specific needs. Generally speaking, you should try to minimize the access permissions of properties and methods, that is, use the private modifier to restrict external access to improve the encapsulation and security of the code. Use the protected modifier only when access is required in subclasses of the class. The public modifier is suitable for properties and methods that need to be accessible both inside and outside the class.

To sum up, there are three types of permission control modifiers in PHP: public, protected and private. They represent public, protected, and private access respectively. Reasonable use of these modifiers can improve the encapsulation, security and maintainability of the code.

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