php入門教程之面向對象

2024-09-04 11:43:36

字體：大中小

來源：轉載

供稿：網友

第一種情況：子類沒有定義構造函數時，默認繼承。

第二種情況：子類定義了構造函數，則不會被繼承。

對于4.x,如果父類恰好定義了子類的同名函數，則會被當做子類的構造函數,實例代碼如下:

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;

上面的代碼在php5中則會調用A而不會調用B()

PHP面向對象:接口實例

我們設計一個在線銷售系統，用戶部分設計如下,將用戶分為，NormalUser, VipUser, InnerUser三種,要求根據用戶的不同折扣計算用戶購買產品的價格,并要求為以后擴展和維護預留空間,用戶部分先聲明了一個接口User,用戶都是User的實現。

user.php代碼如下:

<?

/*

* 定義了 User接口.

* 和子類 NormalUser,VipUser,InnerUser

*/

//User接口,定義了三個抽象方法.

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 = ""; //級別

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";

}

?>

關于產品,我們進行了如下設計,聲明一個接口Product,然后從Product繼承下Book接口,在線銷售的圖書最后是實現了Book接口的BookOnline類。

Product.php代碼如下:

<?

/*與產品相關的類放.*/

Interface Product{ //定義產品接口

public function getProductName();

public function getProductPrice();

}

interface Book extends Product { // book是產品的一個分類

public function getAuthor();

}

class BookOnline implements Book{ // 定義book類.

private $productName; // 產品名

private $productPrice; // 產品價格

private $author; //作者

public function __construct($_bookName){

 $this->productName = $_bookName;

 //這里放置相關初始化的代碼.

 //與數據庫關聯的代碼.

}

public function getProductName(){

 return $this->productName;

}

public function getProductPrice(){

 //這里從數據庫讀取價格.

 //假設價格是 100元.

 $this->productPrice = 100;

 return $this->productPrice;

}

public function getAuthor(){

 //從數據庫里面取值.

 return $this->author;

}

}

?>

關于結算,我們使用了獨立的結算類,使用靜態方法做計算,產品結算,注意參數類型,代碼如下:

<?

include_once("User.php");

include_once("Product.php");

//買了產品到底多少錢呢?

class ProductSettle{

public static function finalPrice(User $_user,Product $_product,$number = 1){

 $price = $_user->getDiscount() * $_product->getProductPrice() * $number;

 return $price;

}

}

?>

下面的例子是實現,大家可以自己分析下,實例代碼如下:

<?

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

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

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

$number = 10;

$book = new BookOnline("設計模式");

$user = new NormalUser("Tom");

$price = ProductSettle::finalPrice($user,$book,$number);

$str = "您好，尊敬的用戶 " . $user->getName() . " ";

$str .= "您的級別是 ". $user->getGrade() .", ";

$str .= "您的折扣是 " . $user->getDiscount() . " ";

$str .= "購買 $number 本《 ". $book->getProductName() ;

$str .= "》的價格是 $price ";

echo $str;

$user = new vipUser("Tom");

$price = ProductSettle::finalPrice($user,$book,$number);

$str = "您好，尊敬的用戶 " . $user->getName() . " ";

$str .= "您的級別是 ". $user->getGrade() .", ";

$str .= "您的折扣是 " . $user->getDiscount() . " ";

$str .= "購買 $number 本《 ". $book->getProductName() ;

$str .= "》的價格是 $price ";

echo $str;

$user = new InnerUser("Tom");

$price = ProductSettle::finalPrice($user,$book,$number);

$str = "您好，尊敬的用戶 " . $user->getName() . " ";

$str .= "您的級別是 ". $user->getGrade() .", ";

$str .= "您的折扣是 " . $user->getDiscount() . " ";

$str .= "購買 $number 本《 ". $book->getProductName() ;

$str .= "》的價格是 $price ";

echo $str;

?>