Detailed explanation of usage examples of object-oriented class constants in PHP

This article mainly introduces PHP object-oriented programming and the like constants usage, which is a very important concept in PHP object-oriented programming, for PHP beginners It is even more necessary to have a firm grasp of it. Friends who need it can refer to

Class constants are a very important concept in PHP object-oriented programming. A firm grasp of class constants will help further improve the efficiency of PHP object-oriented programming. level. This article describes the usage of class constants in PHP programming in the form of examples. The details are as follows:

Class constants: In the class, data that remains unchanged during the running cycle is saved.

Definition:

const 关键字
const 常量名 = 常量值

Examples are as follows:

class Student
{
public $stu_id;
public $stu_name;
public $stu_gender;
const GENDER_MALE= '男';
const GENDER_FEMALE = '女';
}

Class constants are not restricted by access qualification modifiers
Access methods:
Class::Constant name

The example is as follows:

class Student
{
public $stu_id;
public $stu_name;
public $stu_gender;
const GENDER_MALE= '男';
const GENDER_FEMALE = '女';
public function construct($id,$name,$gender='')
{
$this->stu_id= $id;
$this->stu_name= $name;
$this->gender= ($gender == ' ')?self::GENDER_MALE : $gender;
}
}

Summary: The members that can be defined in the class are: constant, staticAttributes, non-static properties, static methods, non-static methods.

Note here:
$this represents the current object, so does it always represent the object of the class where $this belongs?
the answer is negative! Because the value of $this does not depend on the class where $this is located, but depends on the execution object (execution environment) when the method where $this is located is called.

The execution environment of the method, which object the current method is in When executed in an environment, $this in the method indicates which object.

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