PHP introductory tutorial - object-oriented_PHP tutorial-PHP Tutorial-php.cn

In my opinion, object-oriented means various PHP classes, methods, and functions. Now I will introduce to you an introductory tutorial on object-oriented PHP. If you are interested, you can refer to it.

The first case: When the subclass does not define a constructor, it is inherited by default.

Second case: If the subclass defines a constructor, it will not be inherited.

For 4.x, if the parent class happens to define a function with the same name of the subclass, it will be regarded as the constructor of the subclass:

The code is as follows

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代码如下

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class A
{
    function A()
    {
      echo "I am the constructor of A.
n";
    }

    function B()
    {
        echo "I am a regular function named B in class A.
n";
        echo "I am not a constructor in A.
n";
    }
}

class B extends A
{
    function C()
    {
        echo "I am a regular function.
n";
    }
}

//php4 will call B()
$b = new B;

class A
{
function A()
{
echo "I am the constructor of A.
n";
}

function B()
{
echo "I am a regular function named B in class A.
n";
echo "I am not a constructor in A.
n";
}
}

class B extends A
{
function C()
{
echo "I am a regular function.
n";
}
}

//php4 will call B()
$b = new B;

The above code will call A but not B() in php5

PHP object-oriented: interface example

We design an online sales system. The user part is designed as follows:

Divide users into three types: NormalUser, VipUser, and InnerUser.

Requires the calculation of the price of the product purchased by the user based on the user's different discounts.

代码如下

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/*
* 定义了 User接口.
* 和子类 NormalUser,VipUser,InnerUser
*/
//User接口,定义了三个抽象方法.
interface User{
public function getName();
public function setName($_name);
public function getDiscount();
}
abstract class AbstractUser implements User{
private $name = ""; //名字
protected $discount = 0; //折扣
protected $grade = ""; //级别

public function __construct($_name){
$this->setName($_name);
}
public function getName(){
  return $this->name;
}
public function setName($_name){
  $this->name = $_name;
}
public function getDiscount(){
  return $this->discount;
}

public function getGrade(){
  return $this->grade;
}
}
class NormalUser extends AbstractUser {
protected $discount = 1.0;
protected $grade = "NormalUser";
}

class VipUser extends AbstractUser {
protected $discount = 0.8;
protected $grade = "VipUser";
}

class InnerUser extends AbstractUser {
protected $discount = 0.7;
protected $grade = "InnerUser";
}
?>

And ask to reserve space for future expansion and maintenance. The user part first declares an interface User, and users are all implementations of User. user.php

The code is as follows

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/*
* Defines the User interface.
* and subclasses NormalUser, VipUser, InnerUser
*/
//User interface defines three abstract methods.
interface User{
public function getName();
public function setName($_name);
public function getDiscount();
}
abstract class AbstractUser implements User{
private $name = ""; //name
protected $discount = 0; //Discount
protected $grade = ""; //Level

public function __construct($_name){
$this->setName($_name);
}
public function getName(){
return $this->name;
}
public function setName($_name){
$this->name = $_name;
}
public function getDiscount(){
return $this->discount;
}

public function getGrade(){
return $this->grade;
}
}
class NormalUser extends AbstractUser {
protected $discount = 1.0;
protected $grade = "NormalUser";
} class VipUser extends AbstractUser {
protected $discount = 0.8;
protected $grade = "VipUser";
} class InnerUser extends AbstractUser {
protected $discount = 0.7;
protected $grade = "InnerUser";
}
?>

Regarding the product, we have designed it as follows.

Declare an interface Product, and then inherit the Book interface from Product.

The books sold online are finally the BookOnline class that implements the Book interface.

Product.php

The code is as follows

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代码如下

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/*与产品相关的类放.*/
Interface Product{ //定义产品接口
public function getProductName();
public function getProductPrice();
}

interface Book extends Product { // book是产品的一个分类
public function getAuthor();
}

class BookOnline implements Book{ // 定义book类.
private $productName; // 产品名
private $productPrice; // 产品价格
private $author; //作者

public function __construct($_bookName){
$this->productName = $_bookName;
  //这里放置相关初始化的代码.
  //与数据库关联的代码.
}

public function getProductName(){
  return $this->productName;
}

public function getProductPrice(){
  //这里从数据库读取价格.
  //假设价格是 100元.
  $this->productPrice = 100;
  return $this->productPrice;
}

public function getAuthor(){
  //从数据库里面取值.
  return $this->author;
}
}
?>

/*Product-related categories.*/
Interface Product{ //Define product interface
public function getProductName();
public function getProductPrice();
}

interface Book extends Product { // book is a category of product
public function getAuthor();
}

代码如下	复制代码
include_once("User.php"); include_once("Product.php"); //买了产品到底多少钱呢? class ProductSettle{ public static function finalPrice(User $_user,Product $_product,$number = 1){ $price = $_user->getDiscount() * $_product->getProductPrice() * $number; return $price; } } ?>

class BookOnline implements Book{ // Define book class.
private $productName; // product name
private $productPrice; // product price
private $author; //Author

public function __construct($_bookName){
$this->productName = $_bookName;
//Place the relevant initialization code here.
//Code associated with the database.
}

public function getProductName(){
Return $this->productName;
}

public function getProductPrice(){
//Read the price from the database here.
//Suppose the price is 100 yuan.
$this->productPrice = 100;
return $this->productPrice;
}

public function getAuthor(){
//Get the value from the database.
return $this->author;
}
}
?> Regarding settlement, we use an independent settlement class and use static methods to do calculations. Product settlement. Pay attention to parameter types.

The code is as follows	Copy code
include_once("User.php"); include_once("Product.php"); //How much did it cost to buy the product? class ProductSettle{ public static function finalPrice(User $_user,Product $_product,$number = 1){ $price = $_user->getDiscount() * $_product->getProductPrice() * $number; return $price; } } ?>

The example below is the implementation. You can analyze it yourself.

The code is as follows

代码如下

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include_once("./class/User.php");
include_once("./class/Product.php");
include_once("./class/ProductSettle.php");

$number = 10;
$book = new BookOnline("设计模式");

$user = new NormalUser("Tom");
$price = ProductSettle::finalPrice($user,$book,$number);
$str = "您好，尊敬的用户 " . $user->getName() . "
";
$str .= "您的级别是 ". $user->getGrade() .",
";
$str .= "您的折扣是 " . $user->getDiscount() . "
";
$str .= "购买 $number 本《 ". $book->getProductName() ;
$str .= "》的价格是 $price

";
echo $str;

$user = new vipUser("Tom");
$price = ProductSettle::finalPrice($user,$book,$number);
$str = "您好，尊敬的用户 " . $user->getName() . "
";
$str .= "您的级别是 ". $user->getGrade() .",
";
$str .= "您的折扣是 " . $user->getDiscount() . "
";
$str .= "购买 $number 本《 ". $book->getProductName() ;
$str .= "》的价格是 $price

";
echo $str;

$user = new InnerUser("Tom");
$price = ProductSettle::finalPrice($user,$book,$number);
$str = "您好，尊敬的用户 " . $user->getName() . "
";
$str .= "您的级别是 ". $user->getGrade() .",
";
$str .= "您的折扣是 " . $user->getDiscount() . "
";
$str .= "购买 $number 本《 ". $book->getProductName() ;
$str .= "》的价格是 $price

";
echo $str;
?>

Copy code

include_once("./class/User.php");
include_once("./class/Product.php");
include_once("./class/ProductSettle.php");

$number = 10;
$book = new BookOnline("Design Mode");

Related labels：

php under Getting Started Tutorial function object I method kind For

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