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PHP object-oriented concepts and examples_PHP tutorial

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Release： 2016-07-13 17:12:52

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A simple article about PHP object-oriented concepts and examples, friends in need can simply refer to it.

Keywords and special variables
new, class, extends. Everyone knows these three.
::, the scope resolution operator (also known as Paamayim Nekudotayim) or more simply a pair of colons, can be used to access static members, methods and constants. Can also be used to override members and methods in a class.
parent and self. parent refers to the name of the base class pointed to by the derived class in the extends declaration. Doing this avoids using the base class name in multiple places.
$this pseudo variable. $this points to the current instance. $this is not necessarily the object to which the method belongs. Sometimes code within class A will call a static method of class B. Reference example: php.net/manual/zh/language.oop5.basic.php">http://www.php.net/manual/zh/language.oop5.basic.php
static keyword. If you declare a class member or method as static, you can access it directly without instantiating the class. However, except for static methods, static members cannot be accessed through an object. In static methods, $this is not used. Instead use self:: .
final keyword. It can be used on classes and functions, so that classes cannot be inherited and methods cannot be overridden.
Properties
Can be initialized, but the initialized value must be a constant. Use the const keyword in front of a constant. The value of the constant must be a fixed value and cannot be the result of a variable, class attribute or other operation (such as a function call).

Constructor and destructor
Neither of these two functions will secretly call the response function of the base class, which is different from Java's constructor mechanism. To achieve this effect, execution must be displayed. Exceptions cannot be thrown in the destructor.

Abstract class: Class methods declared as abstract cannot contain concrete implementations, and abstract classes cannot be instantiated. Must be inherited first, and then instantiate its subclass. Moreover, the access control of subclasses should be the same as that of abstract classes, or more relaxed. An abstract class contains at least one abstract method.

Interface
Using an interface, you can specify which methods a class must implement without defining the specific content of those methods.
All methods defined must be public and empty
Constants can be defined, but there are no attributes
The implementations of an interface must implement all methods, and can implement multiple interfaces (note that methods cannot have the same name).
Interfaces can be inherited by other interfaces (extends)

The code is as follows

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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";
}
?>

/*<🎜> * 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"; } ?>

Product.php

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; } } ?>

The following example is implemented. 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;
?>

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

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