Classes in PHP - What are classes_PHP Tutorial-PHP Tutorial-php.cn

Classes in PHP - What are classes_PHP Tutorial

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Release： 2016-07-21 16:00:29

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Before elaborating on the concept of classes, let’s first talk about the concept of object-oriented programming: Object-Oriented Programming (OOP) is based on creating software reusable code with the ability to better simulate real-world environments. , which makes it recognized as the winner of top-down programming. It "encapsulates" functions into "objects" necessary for programming by adding extended statements to the program. Object-oriented programming languages make complex work clear and easy to write. It's a revolution, not in the objects themselves, but in their ability to handle work. Objects are not compatible with traditional programming and programming methods, and being partially object-oriented makes the situation worse. Unless the entire development environment is object-oriented, the benefits of objects may not be as great as the trouble. Some people may say that PHP is not a true object-oriented programming language. PHP is a hybrid language. You can use object-oriented programming or traditional procedural programming. However, for the development of large projects, you may want to use pure object-oriented programming in PHP to declare classes, and only use objects and classes in your project development. As projects get larger, it may be helpful to use object-oriented programming. Object-oriented programming code is easy to maintain, easy to understand and reuse, which are the basics of software engineering. Applying these concepts in web-based projects becomes the key to future website success.
Object is an abstraction of something in the problem domain or implementation domain. It reflects the information that this thing needs to save and the role it plays in the system; it is a set of attributes and the right to operate on these attributes. A package of a set of services. Objects should be understood from two aspects: on the one hand, they refer to the objects in the real world that the system needs to process; on the other hand, objects are objects that the computer does not process directly, but processes the corresponding computer representation. This computer representation is also called an object. To put it simply, a person is an object, and a ruler can also be said to be an object. When these objects can be directly represented by data, we call them attributes. The measurement unit of the ruler can be centimeters, meters or feet. This measurement unit is the attribute of the ruler.
In PHP we can define a class. A class refers to a collection of variables and some functions that use these variables. 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:

Copy code The code is as follows:

class Class_name // In object-oriented programming classes, it is customary for the first character of a class to be uppercase and must comply with the naming rules of variables. 
{ 

//A collection of functions and variables 

} 
?>

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

Copy the code The code is as follows:

class Student 
{ 
var $str_Name; //Name 
var $str_Sex; //Gender 
var $int_Id; //Student number 
var $int_English; //English score 
var $int_maths; //Maths scores 
} 
?> 

This is a simple example of a very common definition class, used to display students’ academic performance. The class name is Student, and the Student class includes The basic attributes of a student are: name, gender, student number, English score and math score.
function is called 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 For functions, it can only be local variables. We first define an Input() function to assign an initial value to the object in the instance:

Copy the code The code is as follows:

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 the basic information of students:

Copy code The code is as follows:

function ShowInfo () //Define the ShowInfo() function 
 { 
echo (“Name: $this->str_Name
 
  
”); 
echo (“Student ID: $this->int_Id 
  
”); 
 
”); 
echo (“Math score: $this->int_Maths 
 
”); You must use the new keyword to generate an object: 
$A_student=new Student; 
For example, if we want to create an instance of an object named $Wing and assign a value, we can use the following code: 
$ Wing = new Student; //Use the new keyword to generate objects 
$Wing ->Input (“Wing”, “Male”, 33,95,87); 

//Enter Wing’s name and name respectively. Gender, student number, English scores, and math scores. Name and gender are character variables, so double quotes are required, while other numerical variables do not.
Through the complete source code below, we can clearly see how classes are used in PHP:

Copy code

The code is as follows:

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; int_Maths=$Maths;
}
function ShowInfo()
{
echo ("Name: $this->str_Name

");
echo ("Gender ：$this->str_Sex

”);
echo (“Student ID: $this->int_Id

”); ：$this->int_English

”);
echo (“Math score: $this->int_Maths

”);

$Wing = new Student;
$Wing->Input ("Wing","Male",33,95,87);
$Paladin = new Student;
$Paladin->Input ("paladin","female",38,58,59.5);

$Wing->ShowInfo();
$Paladin->ShowInfo() ;

?>
The execution result should be like this:
Name: Wing
Gender: Male
Student ID: 33
English score: 95
Math score: 87
Name: Paladin
Gender ：Female
Student number: 38
English score: 58
Math score: 59.5

The current version of PHP has much greater support for object-oriented programming than previous versions Improvements, but the support is not yet complete. However, the current support provided by PHP for object-oriented programming languages not only helps us design the structure of the program, but also provides great help for the maintenance of the program.