PHP面向对象程序设计高级特性详解(接口,继承,88bf必发娱乐抽象类,析构,克隆等)

本文实例讲述了PHP面向对象继承用法。分享给大家供大家参考,具体如下:

本文实例讲述了PHP面向对象程序设计高级特性。分享给大家供大家参考,具体如下:

继承

静态属性

先看两个类

<?php
class StaticExample {
  static public $aNum = 0; // 静态共有属性
  static public function sayHello() { // 静态共有方法
    print "hello";
  }
}
print StaticExample::$aNum;
StaticExample::sayHello();
?>
<?php
class CdProduct {
  public $playLength; // 播放时间
  public $title;
  public $producerMainName;
  public $producerFirstName;
  public $price;
  function __construct(  $title, $firstName,
              $mainName, $price,
              $playLength ) {
    $this->title       = $title;
    $this->producerFirstName = $firstName;
    $this->producerMainName = $mainName;
    $this->price       = $price;
    $this->playLength    = $playLength;
  }
  function getPlayLength() {
    return $this->playLength;
  }
  function getSummaryLine() {
    $base = "{$this->title} ( {$this->producerMainName}, ";
    $base .= "{$this->producerFirstName} )";
    $base .= ": playing time - {$this->playLength}";
    return $base;
  }
  function getProducer() {
    return "{$this->producerFirstName}".
        " {$this->producerMainName}";
  }
}
class BookProduct {
  public $numPages; // 看的页数
  public $title;
  public $producerMainName;
  public $producerFirstName;
  public $price;
  function __construct(  $title, $firstName,
              $mainName, $price,
              $numPages ) {
    $this->title       = $title;
    $this->producerFirstName = $firstName;
    $this->producerMainName = $mainName;
    $this->price       = $price;
    $this->numPages     = $numPages;
  }
  function getNumberOfPages() {
    return $this->numPages;
  }
  function getSummaryLine() {
    $base = "{$this->title} ( {$this->producerMainName}, ";
    $base .= "{$this->producerFirstName} )";
    $base .= ": page count - {$this->numPages}";
    return $base;
  }
  function getProducer() {
    return "{$this->producerFirstName}".
        " {$this->producerMainName}";
  }
}
$product1 = new CdProduct("cd1", "bob", "bobbleson", 4, 50 );
print $product1->getSummaryLine();
print "\n";
$product2 = new BookProduct("book1", "harry", "harrelson", 4, 30 );
print $product2->getSummaryLine();
print "\n";
?>

输出:0    hello

输出:

点评:静态属性和方法,可以通过类直接调用。

cd1 ( bobbleson, bob ): playing time – 50
book1 ( harrelson, harry ): page count – 30

SELF

点评:这两个类,代码重复性太高,有相同性,也有差异性。不如用继承来简化处理。

<?php
class StaticExample {
  static public $aNum = 0;
  static public function sayHello() { // 这里的static 和 public的顺序可以颠倒
    self::$aNum++;
    print "hello (".self::$aNum.")\n"; // self 指向当前类, $this指向当前对象。
  }
}
StaticExample::sayHello();
StaticExample::sayHello();
StaticExample::sayHello();
?>

采用继承来处理

输出:

<?php
class ShopProduct {
  public $numPages;
  public $playLength;
  public $title;
  public $producerMainName;
  public $producerFirstName;
  public $price;
  function __construct(  $title, $firstName,
              $mainName, $price,
              $numPages=0, $playLength=0 ) {
    $this->title       = $title;
    $this->producerFirstName = $firstName;
    $this->producerMainName = $mainName;
    $this->price       = $price;
    $this->numPages     = $numPages;
    $this->playLength    = $playLength;
  }
  function getProducer() {
    return "{$this->producerFirstName}".
        " {$this->producerMainName}";
  }
  function getSummaryLine() {
    $base = "$this->title ( {$this->producerMainName}, ";
    $base .= "{$this->producerFirstName} )";
    return $base;
  }
}
class CdProduct extends ShopProduct {
  function getPlayLength() { // 增加属于自己的方法
    return $this->playLength;
  }
  function getSummaryLine() { // 改造了父类的方法
    $base = "{$this->title} ( {$this->producerMainName}, ";
    $base .= "{$this->producerFirstName} )";
    $base .= ": playing time - {$this->playLength}";
    return $base;
  }
}
class BookProduct extends ShopProduct {
  function getNumberOfPages() {
    return $this->numPages;
  }
  function getSummaryLine() {
    $base = "{$this->title} ( {$this->producerMainName}, ";
    $base .= "{$this->producerFirstName} )";
    $base .= ": page count - {$this->numPages}";
    return $base;
  }
}
$product1 = new CdProduct("cd1", "bob", "bobbleson", 4, null, 50 );
print $product1->getSummaryLine();
print "\n";
$product2 = new BookProduct("book1", "harry", "harrelson", 4, 30 );
print $product2->getSummaryLine();
print "\n";
?>
hello (1)
hello (2)
hello (3)

输出:

点评:self 指向当前类,
this指向当前对象。self可以调用当前类的静态属性和方法。this指向当前对象。self可以调用当前类的静态属性和方法。this可以调用当前类的正常属性和方法。

cd1 ( bobbleson, bob ): playing time – 50
book1 ( harrelson, harry ): page count – 30

常量属性

点评:继承处理很好的解决了差异性,相通性问题。

<?php
class ShopProduct {
  const AVAILABLE   = 0; // 只能用大写字母命名常量
  const OUT_OF_STOCK  = 1;
  public $status;
}
print ShopProduct::AVAILABLE;
?>

进一步优化处理

输出:0

<?php
class ShopProduct {
  // 抽离出共有属性
  public $title;
  public $producerMainName;
  public $producerFirstName;
  public $price;
  function __construct(  $title, $firstName,
              $mainName, $price ) {
    $this->title       = $title;
    $this->producerFirstName = $firstName;
    $this->producerMainName = $mainName;
    $this->price       = $price;
  }
  function getProducer() {
    return "{$this->producerFirstName}".
        " {$this->producerMainName}";
  }
  function getSummaryLine() {
    $base = "{$this->title} ( {$this->producerMainName}, ";
    $base .= "{$this->producerFirstName} )";
    return $base;
  }
}
class CdProduct extends ShopProduct {
  // 抽离出属于自己特有的属性
  public $playLength;
  function __construct(  $title, $firstName,
              $mainName, $price, $playLength ) {
    parent::__construct(  $title, $firstName,
                $mainName, $price ); // 继承父类的构造函数
    $this->playLength = $playLength; // 处理自己专有的属性
  }
  function getPlayLength() {
    return $this->playLength;
  }
  function getSummaryLine() {
    $base = "{$this->title} ( {$this->producerMainName}, ";
    $base .= "{$this->producerFirstName} )";
    $base .= ": playing time - {$this->playLength}";
    return $base;
  }
}
class BookProduct extends ShopProduct {
  public $numPages;
  function __construct(  $title, $firstName,
              $mainName, $price, $numPages ) {
    parent::__construct(  $title, $firstName,
                $mainName, $price );
    $this->numPages = $numPages;
  }
  function getNumberOfPages() {
    return $this->numPages;
  }
  function getSummaryLine() {
    $base = "$this->title ( $this->producerMainName, ";
    $base .= "$this->producerFirstName )";
    $base .= ": page count - $this->numPages";
    return $base;
  }
}
$product1 = new CdProduct("cd1", "bob", "bobbleson", 4, 50 );
print $product1->getSummaryLine();
print "\n";
$product2 = new BookProduct("book1", "harry", "harrelson", 4, 30 );
print $product2->getSummaryLine();
print "\n";
?>

点评:常量只能用大写字母,并且可以通过类直接调用。

输出:

接口

cd1 ( bobbleson, bob ): playing time – 50
book1 ( harrelson, harry ): page count – 30

<?php
interface Chargeable { // 接口,抽象类是介于基类与接口之间的东西
  public function getPrice();
}
class ShopProduct implements Chargeable {
  // ...
  protected $price;
  // ...
  public function getPrice() {
    return $this->price;
  }
  // ...
}
$product = new ShopProduct();
?>

点评:这里把共有属性在父类中,其他个性属性放在自己的类中处理。并设置自己的构造方法,继承父类的构造方法。

如果没有实现getPrice方法,将会报错。

进一步继承父类的方法

Fatal error: Class ShopProduct contains 1
abstract method and must therefore be declared abstract or implement the
remaining methods (Chargeable::getPrice)

<?php
class ShopProduct {
  public $title;
  public $producerMainName;
  public $producerFirstName;
  public $price;
  function __construct(  $title, $firstName,
              $mainName, $price ) {
    $this->title       = $title;
    $this->producerFirstName = $firstName;
    $this->producerMainName = $mainName;
    $this->price       = $price;
  }
  function getProducer() {
    return "{$this->producerFirstName}".
        " {$this->producerMainName}";
  }
  function getSummaryLine() {
    $base = "{$this->title} ( {$this->producerMainName}, ";
    $base .= "{$this->producerFirstName} )";
    return $base;
  }
}
class CdProduct extends ShopProduct {
  public $playLength;
  function __construct(  $title, $firstName,
              $mainName, $price, $playLength ) {
    parent::__construct(  $title, $firstName,
                $mainName, $price );
    $this->playLength = $playLength;
  }
  function getPlayLength() {
    return $this->playLength;
  }
  function getSummaryLine() {
    $base = parent::getSummaryLine();
    $base .= ": playing time - {$this->playLength}";
    return $base;
  }
}
class BookProduct extends ShopProduct {
  public $numPages;
  function __construct(  $title, $firstName,
              $mainName, $price, $numPages ) {
    parent::__construct(  $title, $firstName,
                $mainName, $price );
    $this->numPages = $numPages;
  }
  function getNumberOfPages() {
    return $this->numPages;
  }
  function getSummaryLine() {
    $base = parent::getSummaryLine();
    $base .= ": page count - {$this->numPages}";
    return $base;
  }
}
$product1 = new CdProduct("cd1", "bob", "bobbleson", 4, 50 );
print $product1->getSummaryLine();
print "\n";
$product2 = new BookProduct("book1", "harry", "harrelson", 4, 30 );
print $product2->getSummaryLine();
print "\n";
?>

继承类与接口

输出:

<?php
class TimedService{ }
interface Bookable{ }
interface Chargeable{ }
class Consultancy extends TimedService implements Bookable, Chargeable { // 继承类与接口
  // ...
}
?>

cd1 ( bobbleson, bob ): playing time – 50
book1 ( harrelson, harry ): page count – 30

抽象类

点评:同样的结果,可以优化优化再优化。这里继承父类的方法。parent::getSummaryLine()。不过这个用的比较少。

先来看一段代码

继续添加一些有意思的内容

<?php
abstract class DomainObject {
}
class User extends DomainObject {
  public static function create() {
    return new User();
  }
}
class Document extends DomainObject {
  public static function create() {
    return new Document();
  }
}
$document = Document::create();
print_r( $document );
?>
<?php
class ShopProduct {
  private $title;
  private $discount = 0;
  private $producerMainName;
  private $producerFirstName;
  protected $price;
  function __construct(  $title, $firstName,
              $mainName, $price ) {
    $this->title       = $title;
    $this->producerFirstName = $firstName;
    $this->producerMainName = $mainName;
    $this->price       = $price;
  }
  function setDiscount( $num ) {
    $this->discount=$num;
  }
  function getPrice() {
    return ($this->price - $this->discount);
  }
  function getProducer() {
    return "{$this->producerFirstName}".
        " {$this->producerMainName}";
  }
  function getSummaryLine() {
    $base = "{$this->title} ( {$this->producerMainName}, ";
    $base .= "{$this->producerFirstName} )";
    return $base;
  }
}
class CdProduct extends ShopProduct {
  public $playLength;
  function __construct(  $title, $firstName,
              $mainName, $price, $playLength ) {
    parent::__construct(  $title, $firstName,
                $mainName, $price );
    $this->playLength = $playLength;
  }
  function getPlayLength() {
    return $this->playLength;
  }
  function getSummaryLine() {
    $base = parent::getSummaryLine();
    $base .= ": playing time - {$this->playLength}";
    return $base;
  }
}
class BookProduct extends ShopProduct {
  public $numPages;
  function __construct(  $title, $firstName,
              $mainName, $price, $numPages ) {
    parent::__construct(  $title, $firstName,
                $mainName, $price );
    $this->numPages = $numPages;
  }
  function getPrice() {
    return $this->price;
  }
  function getNumberOfPages() {
    return $this->numPages;
  }
  function getSummaryLine() {
    $base = parent::getSummaryLine();
    $base .= ": page count - {$this->numPages}";
    return $base;
  }
}
$product1 = new CdProduct("cd1", "bob", "bobbleson", 4, 50 );
$product1->setDiscount( 3 );
print $product1->getSummaryLine();
print "\n";
print "price: {$product1->getPrice()}\n";
$product2 = new BookProduct("book1", "harry", "harrelson", 4, 30 );
$product2->setDiscount( 3 ); // 折扣对book无效
print $product2->getSummaryLine();
print "\n";
print "price: {$product2->getPrice()}\n";
?>

输出:

输出:

Document Object
(
)

cd1 ( bobbleson, bob ): playing time – 50
price: 1
book1 ( harrelson, harry ): page count – 30
price: 4

静态方法

点评:父类添加了折扣,book继承之后,修改了getPrice方法,所以折扣对book无效。

<?php
abstract class DomainObject {
  private $group; // 私有属性group
  public function __construct() {
    $this->group = static::getGroup();//static 静态类
  }
  public static function create() {
    return new static();
  }
  static function getGroup() { // 静态方法
    return "default";
  }
}
class User extends DomainObject {
}
class Document extends DomainObject {
  static function getGroup() { // 改变了内容
    return "document";
  }
}
class SpreadSheet extends Document { // 继承之后,group也就与document相同了
}
print_r(User::create());
print_r(SpreadSheet::create());
?>

私有化属性,通过方法来设置与获取

输出:

<?php
class ShopProduct {
  // 私有化属性,通过方法来设置与获取
  private $title;
  private $producerMainName;
  private $producerFirstName;
  protected $price;
  private $discount = 0;
  public function __construct(  $title, $firstName,
              $mainName, $price ) {
    $this->title       = $title;
    $this->producerFirstName = $firstName;
    $this->producerMainName = $mainName;
    $this->price       = $price;
  }
  public function getProducerFirstName() {
    return $this->producerFirstName;
  }
  public function getProducerMainName() {
    return $this->producerMainName;
  }
  public function setDiscount( $num ) {
    $this->discount=$num;
  }
  public function getDiscount() {
    return $this->discount;
  }
  public function getTitle() {
    return $this->title;
  }
  public function getPrice() {
    return ($this->price - $this->discount);
  }
  public function getProducer() {
    return "{$this->producerFirstName}".
        " {$this->producerMainName}";
  }
  public function getSummaryLine() {
    $base = "{$this->title} ( {$this->producerMainName}, ";
    $base .= "{$this->producerFirstName} )";
    return $base;
  }
}
class CdProduct extends ShopProduct {
  private $playLength = 0;
  public function __construct(  $title, $firstName,
              $mainName, $price, $playLength ) {
    parent::__construct(  $title, $firstName,
                $mainName, $price );
    $this->playLength = $playLength;
  }
  public function getPlayLength() {
    return $this->playLength;
  }
  public function getSummaryLine() {
    $base = parent::getSummaryLine();
    $base .= ": playing time - {$this->playLength}";
    return $base;
  }
}
class BookProduct extends ShopProduct {
  private $numPages = 0;
  public function __construct(  $title, $firstName,
              $mainName, $price, $numPages ) {
    parent::__construct(  $title, $firstName,
                $mainName, $price );
    $this->numPages = $numPages;
  }
  public function getNumberOfPages() {
    return $this->numPages;
  }
  public function getSummaryLine() {
    $base = parent::getSummaryLine();
    $base .= ": page count - {$this->numPages}";
    return $base;
  }
  public function getPrice() {
    return $this->price;
  }
}
$product1 = new CdProduct("cd1", "bob", "bobbleson", 4, 50 );
print $product1->getSummaryLine()."\n";
$product2 = new BookProduct("book1", "harry", "harrelson", 4, 30 );
print $product2->getSummaryLine()."\n";
?>
User Object
(
  [group:DomainObject:private] => default
)
SpreadSheet Object
(
  [group:DomainObject:private] => document
)

输出:

final字段

cd1 ( bobbleson, bob ): playing time – 50
book1 ( harrelson, harry ): page count – 30

使类无法被继承,用的不多

点评:这里进一步私有化了属性,要想获取只能通过方法。这样就确保了安全性。

<?php
final class Checkout { // 终止类的继承
  // ...
}
class IllegalCheckout extends Checkout {
  // ...
}
$checkout = new Checkout();
?>

更多关于PHP相关内容感兴趣的读者可查看本站专题:《php面向对象程序设计入门教程》、《PHP基本语法入门教程》、《PHP运算与运算符用法总结》、《PHP网络编程技巧总结》、《PHP数组(Array)操作技巧大全》、《php字符串(string)用法总结》、《php+mysql数据库操作入门教程》及《php常见数据库操作技巧汇总

输出:

希望本文所述对大家PHP程序设计有所帮助。

Fatal error: Class IllegalCheckout may not
inherit from final class (Checkout)

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final方法不能够被重写

<?php
class Checkout {
  final function totalize() {
    // calculate bill
  }
}
class IllegalCheckout extends Checkout {
  function totalize() { // 不能重写final方法
    // change bill calculation
  }
}
$checkout = new Checkout();
?>

输出:

Fatal error: Cannot override final method
Checkout::totalize()

析构函数

<?php
class Person {
  protected $name;
  private $age;
  private $id;
  function __construct( $name, $age ) {
    $this->name = $name;
    $this->age = $age;
  }
  function setId( $id ) {
    $this->id = $id;
  }
  function __destruct() { // 析构函数
    if ( ! empty( $this->id ) ) {
      // save Person data
      print "saving person\n";
    }
    if ( empty( $this->id ) ) {
      // save Person data
      print "do nothing\n";
    }
  }
}
$person = new Person( "bob", 44 );
$person->setId( 343 );
$person->setId( '' ); // 最后执行析构函数,使用完之后执行
?>

输出:

do nothing

__clone方法

克隆的时候执行

<?php
class Person {
  private $name;
  private $age;
  private $id;
  function __construct( $name, $age ) {
    $this->name = $name;
    $this->age = $age;
  }
  function setId( $id ) {
    $this->id = $id;
  }
  function __clone() { // 克隆时候执行
    $this->id = 0;
  }
}
$person = new Person( "bob", 44 );
$person->setId( 343 );
$person2 = clone $person;
print_r( $person );
print_r( $person2 );
?>

输出:

Person Object
(
  [name:Person:private] => bob
  [age:Person:private] => 44
  [id:Person:private] => 343
)
Person Object
(
  [name:Person:private] => bob
  [age:Person:private] => 44
  [id:Person:private] => 0
)

再看一个例子

<?php
class Account { // 账户类
  public $balance; // 余额
  function __construct( $balance ) {
    $this->balance = $balance;
  }
}
class Person {
  private $name;
  private $age;
  private $id;
  public $account;
  function __construct( $name, $age, Account $account ) {
    $this->name = $name;
    $this->age = $age;
    $this->account = $account;
  }
  function setId( $id ) {
    $this->id = $id;
  }
  function __clone() {
    $this->id  = 0;
  }
}
$person = new Person( "bob", 44, new Account( 200 ) ); // 以类对象作为参数
$person->setId( 343 );
$person2 = clone $person;
// give $person some money
$person->account->balance += 10;
// $person2 sees the credit too
print $person2->account->balance; // person的属性account也是一个类,他的属性balance的值是210
// output:
// 210
?>

点评:学习还是能够开拓大脑的,今天终于明白为什么有多个箭头的概念了$person->account->balance。这里的account属性是一个对象。

__toString

<?php
class Person {
  function getName() { return "Bob"; }
  function getAge() { return 44; }
  function __toString() {
    $desc = $this->getName()." (age ";
    $desc .= $this->getAge().")";
    return $desc;
  }
}
$person = new Person();
print $person; // 打印时候集中处理
// Bob (age 44)
?>

点评:必须是print或echo时才有效,print_r就输出对象。

Person Object()

更多关于PHP相关内容感兴趣的读者可查看本站专题:《php面向对象程序设计入门教程》、《PHP基本语法入门教程》、《PHP运算与运算符用法总结》、《PHP网络编程技巧总结》、《PHP数组(Array)操作技巧大全》、《php字符串(string)用法总结》、《php+mysql数据库操作入门教程》及《php常见数据库操作技巧汇总

希望本文所述对大家PHP程序设计有所帮助。

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