Detailed explanation of PHP permission control modifiers: Comprehensive understanding of commonly used permission control modifiers

Detailed explanation of PHP permission control modifiers: To fully understand the commonly used permission control modifiers, specific code examples are required

In PHP development, permission control is a very important concept, which can effectively ensure the security and maintainability of the code. In permission control, modifiers are essential elements. There are three modifiers in PHP: public, protected and private, which respectively represent three access rights. This article will introduce their usage and usage scenarios in detail, and provide specific code examples to help readers better understand.

1. public modifier

The public modifier is the most widely used permission modifier. After adding the public modifier before the properties or methods in the class, they will will become public and can be accessed both inside and outside the class. The following is an example:

class Person {
  public $name;

  public function sayHello() {
    echo 'Hello！我的名字是' . $this->name;
  }
}

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

Through the above code, we create a Person class and define a public property $name and a public method sayHello() inside it. By assigning a value to the $name attribute and calling the sayHello() method, the value of the attribute can be obtained and modified externally, and the corresponding method can be called.

2. protected modifier

protected modifier is limited to the interior of the class and subclasses of the class. It can be used to protect the attributes or methods of the class to avoid being accessed by external The code can be accessed or modified at will. The following is an example:

class Person {
  protected $name;

  protected function sayHello() {
    echo 'Hello！我的名字是' . $this->name;
  }
}

class Student extends Person {
  public function introduce() {
    echo '我是' . $this->name . '，来自阿凡达星球';
  }
}

$student = new Student();
$student->name = 'Lucy'; //会出错
$student->introduce();

As you can see from the above example, we created a new class Student and inherited the Person class. A protected $name attribute and a protected sayHello() method are defined in the Person class, and in the Student class, we define a public introduce() method to display the $name attribute. Since in the Student class The $name property cannot be accessed directly, so the wrong value is assigned to it. This way, $name is not leaked to other parts of the code.

3. private modifier

The private modifier is more strict and can only be accessed within the class and cannot be accessed by external code or subclasses of the class. The following is an example:

class Person {
  private $name;

  private function sayHello() {
    echo 'Hello！我的名字是' . $this->name;
  }
}

$person = new Person();
$person->name = 'Lily'; //会出错
$person->sayHello();    //会出错

As you can see from the above example, we created a Person class and defined a private property $name and a private method sayHello() inside it. Since both $name and sayHello() are set as private, they are not accessible from the outside and any attempt to access them from external code will result in an error.

Summary

Through the above examples, we can see the usage and usage scenarios of the three modifiers, which respectively correspond to the three access rights of public, protected and private. In PHP development, reasonable use of permission control modifiers can not only improve the maintainability and security of the code, but also effectively prevent errors and bugs in the code.

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