What are classes and objects in PHP? Why learn object-oriented? how to use?

The previous article introduced to you "What is pdo in PHP? What are the advantages of accessing a database? What does extension do? 》, this article continues to introduce to you what are classes and objects in PHP? Why learn object-oriented? how to use? It has certain reference value. Friends in need can refer to it. I hope it will be helpful to everyone.

PHP Advanced Syntax - Classes and Objects

1. Why learn object-oriented

Object-oriented thinking is a highly abstract form of human thought.

After learning object-oriented, our code will be very elegant and compact

We only need one or two lines of code to complete some functions

2 , process-oriented and object-oriented

The codes we wrote before were all process-oriented

Building a house:

1. Laying the foundation

2. Building a house

3. Decoration

Object-oriented thinking:

1. New an object, the object calls the foundation method

2. new A contractor, let him build a house

3. new-a decoration worker, let him decorate

Everything is an object, and multiple objects work together to complete our function.

In the future, our thinking must change to object-oriented.

Syntax level: encapsulation, inheritance, polymorphism

Ideological aspect

3. Classes and objects in life

Human beings :Abstract concept

Object: Kobe, Wade

Class is an abstract concept, object is the concrete thing

Car Your Land Rover

Computer Your Computer

Official Concept: A class is the abstraction of an object, and an object is the concrete representation of a class

4. Simple use of classes

Attributes and Behavior

• Property===》Variable

• Behavior===》Method

Naming specification

Class names follow the big camel case principle

persontest ====>
PersonTest====> personTest

Create object method

//Create an object through the new keyword, after person You can add parentheses or not. It is recommended that everyone

add

//The first method of object creation

$xiaoming = new Person() ;
//var_dump ($xiaoming) ;

//The second method of object creation, Create objects through class name strings

$className ='Persoin' ;
$xiaoli = new $className () ;
var_dump($xiaoli) ;

Object access properties and methods

$xiaoming->name = '小明' ;
$xiaoming-> love () ;

For the simple use of classes, we write through PHP syntax, first starting with class as the keyword, We write the class name with person. At this time, we will have attributes and methods in the class. Let’s take the code as an example:

<?php
class Person 
{
        public $age;
        public function like( )
        {
            echo &#39;我喜欢你&#39;;
        }
}
$xiaoming = new Person() ;
var_dump($xiaoming) ;
?>

The code displays the result:

<?php
class Person 
{
        public $age;
        public function like( )
        {
            echo &#39;我喜欢你&#39;;
        }
}
//$xiaoming = new Person() ;
$name = &#39;Person&#39;;
$xiaoming = new $name();
//var_dump($xiaoming) ;
$xiaoming->like();
?>

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