What is the underline before the php method?

PHP is a widely used programming language that can be used to create web applications. In PHP, you sometimes see an underscore before a method. What does this underscore mean?

In PHP, an underscore in front of a method generally indicates that the method is a private method. Private methods can only be used within the class and cannot be called outside the class. The use of this method can help us control program accessibility and prevent external malicious interference.

When we define a method as a private method, the method can only be called by internal methods of the class. If we try to call it from outside the class, we get an "unable to access private method" error. This ensures that the method can only be called by other methods of the class.

On the other hand, PHP also provides another type of method - protection method. Like private methods, protected methods can only be accessed within the class. But unlike private methods, protected methods can also be called by subclasses of the class. The use of this method can prevent method calls in the subclass from conflicting with methods in the parent class, and enhance the maintainability and scalability of the program.

In PHP, naming rules: In order to avoid conflicts with system functions or keywords, we recommend that users add an underscore "_" in front of the function or method name when defining a function or method name.

For example:

class test{
    private function _test(){
        echo "this is a test!";
    }
}

The _test() method in the above code is a private method and can only be used within the class. If we try to call it from outside the class, we'll get an error.

In actual programming, private methods and protected methods are powerful tools used to control program access. By using them, we can better protect the security and stability of the program and prevent unnecessary interference. At the same time, in order to avoid conflicts with system functions or keywords, we must follow naming rules and add an underscore before the function name or method name to ensure the normal operation of the program.

In short, adding an underline before a PHP method simply and clearly indicates that the access permission of the method is a private method, which helps to improve the reliability and security of the program while avoiding conflicts with system functions or keywords. . As developers, we should make full use of this language feature, optimize the program architecture, and create a more stable and reliable system.

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