What does class in php mean?

In PHP, a class (Class) is a collection of variables and functions that act on these variables. It is a collection of objects with the same attributes and operations. It provides a unified abstract description for all objects belonging to this class, which includes two main parts: attributes and operations.

PHP is a loosely typed language, so overloading by type does not work, nor does overloading by different numbers of parameters. Sometimes it's good to overload constructors in an orientation so that you can create objects in different ways (passing different numbers of arguments). In PHP, this is achieved through classes.

In PHP, information encapsulation is completed through classes. The syntax for defining a class in PHP is:

<?php
class Class_name       // 在面向对象编程类中，习惯上类的第一个字符为大写，并且必须符合变量的命名规则。
{
//函数与变量的集合
}
?>

When defining a class, you can define it in the format of your own preference, but It is best to maintain a standard so that development will be more efficient.
Data members are defined using the "var" declaration in the class. Before assigning values ​​to the data members, they have no type. A data member can be an integer, an array, an associated array (Associative Array) or an object.
The following is a practical example of a class definition:

<?php 
class Student 
{
var $str_Name; //姓名
var $str_Sex; //性别
var $int_Id; //学号
var $int_English;  //英语成绩
var $int_maths; //数学成绩
}
?>

This is a simple example of a very common class definition, used to display students’ academic performance. The class name is Student, and the Student class covers it A student's basic attributes: name, gender, student number, English score and math score.

function We call it a function defined in a class. When accessing class member variables in a function, you should use $this->var_name, where var_name refers to the variable declared in the class. Otherwise, for a function, it can only be a local variable. We first define an Input() function to assign an initial value to the object in the instance:

function  Input ( $Name, $Sex, $Id, $Englis, $Maths)
{
         $this->str_Name=$Name;
         $this->str_Sex =$Sex;
         $this->int_Id =$Id;
         $this->int_Englis=$English;
$this->int_Maths=$Maths;
       }

Now we define a function called "ShowInfo()" to print students The basic situation:

function ShowInfo()  //定义ShowInfo()函数
    {
echo (“姓名：$this->str_Name<br> 
”);
echo (“性别：$this->str_Sex <br> 
”);
echo (“学号：$this->int_Id <br> 
”);
echo (“英语成绩：$this->int_English <br> 
”);
echo (“数学成绩：$this->int_Maths <br> 
”);
    }

The defined class must use the new keyword to generate the object:

$A_student=new Student;

For example, we want to create an instance for an object named $Wing, And for assignment, you can use the following code:

$Wing =new Student;  //用new关键词来生成对象
$Wing ->Input (“Wing”,”男”,33,95,87); 
//分别输入Wing的姓名、性别、学号、英语成绩、数学成绩，其中姓名和性别是字符型变量，所以需要用双引号，其它为数值型变量则不需要。

Through the complete source code below, we can clearly see how classes are used in PHP:

<?php 
class Student 
{
var $str_Name; 
var $str_Sex; 
var $int_Id; 
var $int_English;  
var $int_maths; 
    function  Input ( $Name, $Sex, $Id, $English, $Maths)
       {
         $this->str_Name=$Name;
         $this->str_Sex =$Sex;
         $this->int_Id =$Id;
         $this->int_English=$English;
$this->int_Maths=$Maths;
} 
function ShowInfo()  
    {
echo (“姓名：$this->str_Name<br> 
”);
echo (“性别：$this->str_Sex <br> 
”);
echo (“学号：$this->int_Id <br> 
”);
echo (“英语成绩：$this->int_English <br> 
”);
echo (“数学成绩：$this->int_Maths <br> 
”);
    }
   } 
  $Wing = new Student;
  $Wing->Input (“Wing”,”男”,33,95,87);
  $Paladin = new Student;
  $Paladin->Input (“paladin”,”女”,38,58,59.5);
$Wing->ShowInfo();
$Paladin->ShowInfo();
?>

The execution result should be like this:

姓名：Wing
性别：男 
学号：33 
英语成绩：95 
数学成绩：87 
姓名：Paladin
性别：女 
学号：38 
英语成绩：58 
数学成绩：59.5

The existing version of PHP has greatly improved its support for object-oriented programming compared with previous versions, but it supports It is not complete yet, but the support provided by PHP for object-oriented programming languages ​​at this stage is not only helpful for us to design the structure of the program, but also provides great help for the maintenance of the program.

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