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PHP面向对象继承用法是什么，有什么技巧

时间2024-03-22 22:08:03发布访客分类PHP浏览824
导读：这篇文章分享给大家的内容是关于PHP面向对象继承用法是什么，有什么技巧，本文介绍得很详细，内容很有参考价值，希望可以帮到有需要的小伙伴，接下来就让小编带领大家一起了解看看吧。 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，...
这篇文章分享给大家的内容是关于PHP面向对象继承用法是什么，有什么技巧，本文介绍得很详细，内容很有参考价值，希望可以帮到有需要的小伙伴，接下来就让小编带领大家一起了解看看吧。

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：

继承

先看两个类

?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：

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

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。

采用继承来处理

?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";
    
?>

输出：

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

点评：继承处理很好的解决了差异性，相通性问题。

进一步优化处理

?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";
    
?>

输出：

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

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。

进一步继承父类的方法

?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";
    
?>

输出：

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

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。

继续添加一些有意思的内容

?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：

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

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。

私有化属性，通过方法来设置与获取

?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";
    
?>

输出：

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

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。


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