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PHP教程：PHP面向对象继承用法详解(优化与减少代码重复)

作者：VEPHP   时间 2017-09-22

《PHP教程：PHP面向对象继承用法详解(优化与减少代码重复)》要点：
本文介绍了PHP教程：PHP面向对象继承用法详解(优化与减少代码重复)，希望对您有用。如果有疑问，可以联系我们。

PHP编程本文实例讲述了PHP面向对象继承用法.分享给大家供大家参考,具体如下：

PHP编程继承

PHP编程先看两个类

  1. PHP编程
  2. <?php
  3. class CdProduct {
  4.   public $playLength; // 播放时间
  5.   public $title;
  6.   public $producerMainName;
  7.   public $producerFirstName;
  8.   public $price;
  9.   function __construct(  $title, $firstName,
  10.               $mainName, $price,
  11.               $playLength ) {
  12.     $this->title       = $title;
  13.     $this->producerFirstName = $firstName;
  14.     $this->producerMainName = $mainName;
  15.     $this->price       = $price;
  16.     $this->playLength    = $playLength;
  17.   }
  18.   function getPlayLength() {
  19.     return $this->playLength;
  20.   }
  21.   function getSummaryLine() {
  22.     $base = "{$this->title} ( {$this->producerMainName}, ";
  23.     $base .= "{$this->producerFirstName} )";
  24.     $base .= ": playing time - {$this->playLength}";
  25.     return $base;
  26.   }
  27.   function getProducer() {
  28.     return "{$this->producerFirstName}".
  29.         " {$this->producerMainName}";
  30.   }
  31. }
  32. class BookProduct {
  33.   public $numPages; // 看的页数
  34.   public $title;
  35.   public $producerMainName;
  36.   public $producerFirstName;
  37.   public $price;
  38.   function __construct(  $title, $firstName,
  39.               $mainName, $price,
  40.               $numPages ) {
  41.     $this->title       = $title;
  42.     $this->producerFirstName = $firstName;
  43.     $this->producerMainName = $mainName;
  44.     $this->price       = $price;
  45.     $this->numPages     = $numPages;
  46.   }
  47.   function getNumberOfPages() {
  48.     return $this->numPages;
  49.   }
  50.   function getSummaryLine() {
  51.     $base = "{$this->title} ( {$this->producerMainName}, ";
  52.     $base .= "{$this->producerFirstName} )";
  53.     $base .= ": page count - {$this->numPages}";
  54.     return $base;
  55.   }
  56.   function getProducer() {
  57.     return "{$this->producerFirstName}".
  58.         " {$this->producerMainName}";
  59.   }
  60. }
  61. $product1 = new CdProduct("cd1", "bob", "bobbleson", 4, 50 );
  62. print $product1->getSummaryLine();
  63. print "\n";
  64. $product2 = new BookProduct("book1", "harry", "harrelson", 4, 30 );
  65. print $product2->getSummaryLine();
  66. print "\n";
  67. ?>

PHP编程输出：

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

PHP编程点评：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编程采用继承来处理

  1. PHP编程
  2. <?php
  3. class ShopProduct {
  4.   public $numPages;
  5.   public $playLength;
  6.   public $title;
  7.   public $producerMainName;
  8.   public $producerFirstName;
  9.   public $price;
  10.   function __construct(  $title, $firstName,
  11.               $mainName, $price,
  12.               $numPages=0, $playLength=0 ) {
  13.     $this->title       = $title;
  14.     $this->producerFirstName = $firstName;
  15.     $this->producerMainName = $mainName;
  16.     $this->price       = $price;
  17.     $this->numPages     = $numPages;
  18.     $this->playLength    = $playLength;
  19.   }
  20.   function getProducer() {
  21.     return "{$this->producerFirstName}".
  22.         " {$this->producerMainName}";
  23.   }
  24.   function getSummaryLine() {
  25.     $base = "$this->title ( {$this->producerMainName}, ";
  26.     $base .= "{$this->producerFirstName} )";
  27.     return $base;
  28.   }
  29. }
  30. class CdProduct extends ShopProduct {
  31.   function getPlayLength() { // 增加属于自己的方法
  32.     return $this->playLength;
  33.   }
  34.   function getSummaryLine() { // 改造了父类的方法
  35.     $base = "{$this->title} ( {$this->producerMainName}, ";
  36.     $base .= "{$this->producerFirstName} )";
  37.     $base .= ": playing time - {$this->playLength}";
  38.     return $base;
  39.   }
  40. }
  41. class BookProduct extends ShopProduct {
  42.   function getNumberOfPages() {
  43.     return $this->numPages;
  44.   }
  45.   function getSummaryLine() {
  46.     $base = "{$this->title} ( {$this->producerMainName}, ";
  47.     $base .= "{$this->producerFirstName} )";
  48.     $base .= ": page count - {$this->numPages}";
  49.     return $base;
  50.   }
  51. }
  52. $product1 = new CdProduct("cd1", "bob", "bobbleson", 4, null, 50 );
  53. print $product1->getSummaryLine();
  54. print "\n";
  55. $product2 = new BookProduct("book1", "harry", "harrelson", 4, 30 );
  56. print $product2->getSummaryLine();
  57. print "\n";
  58. ?>

PHP编程输出：

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

PHP编程点评：继承处理很好的解决了差异性,相通性问题.

PHP编程进一步优化处理

  1. PHP编程
  2. <?php
  3. class ShopProduct {
  4.   // 抽离出共有属性
  5.   public $title;
  6.   public $producerMainName;
  7.   public $producerFirstName;
  8.   public $price;
  9.   function __construct(  $title, $firstName,
  10.               $mainName, $price ) {
  11.     $this->title       = $title;
  12.     $this->producerFirstName = $firstName;
  13.     $this->producerMainName = $mainName;
  14.     $this->price       = $price;
  15.   }
  16.   function getProducer() {
  17.     return "{$this->producerFirstName}".
  18.         " {$this->producerMainName}";
  19.   }
  20.   function getSummaryLine() {
  21.     $base = "{$this->title} ( {$this->producerMainName}, ";
  22.     $base .= "{$this->producerFirstName} )";
  23.     return $base;
  24.   }
  25. }
  26. class CdProduct extends ShopProduct {
  27.   // 抽离出属于自己特有的属性
  28.   public $playLength;
  29.   function __construct(  $title, $firstName,
  30.               $mainName, $price, $playLength ) {
  31.     parent::__construct(  $title, $firstName,
  32.                 $mainName, $price ); // 继承父类的构造函数
  33.     $this->playLength = $playLength; // 处理自己专有的属性
  34.   }
  35.   function getPlayLength() {
  36.     return $this->playLength;
  37.   }
  38.   function getSummaryLine() {
  39.     $base = "{$this->title} ( {$this->producerMainName}, ";
  40.     $base .= "{$this->producerFirstName} )";
  41.     $base .= ": playing time - {$this->playLength}";
  42.     return $base;
  43.   }
  44. }
  45. class BookProduct extends ShopProduct {
  46.   public $numPages;
  47.   function __construct(  $title, $firstName,
  48.               $mainName, $price, $numPages ) {
  49.     parent::__construct(  $title, $firstName,
  50.                 $mainName, $price );
  51.     $this->numPages = $numPages;
  52.   }
  53.   function getNumberOfPages() {
  54.     return $this->numPages;
  55.   }
  56.   function getSummaryLine() {
  57.     $base = "$this->title ( $this->producerMainName, ";
  58.     $base .= "$this->producerFirstName )";
  59.     $base .= ": page count - $this->numPages";
  60.     return $base;
  61.   }
  62. }
  63. $product1 = new CdProduct("cd1", "bob", "bobbleson", 4, 50 );
  64. print $product1->getSummaryLine();
  65. print "\n";
  66. $product2 = new BookProduct("book1", "harry", "harrelson", 4, 30 );
  67. print $product2->getSummaryLine();
  68. print "\n";
  69. ?>

PHP编程输出：

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

PHP编程点评：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.

PHP编程进一步继承父类的方法

  1. PHP编程
  2. <?php
  3. class ShopProduct {
  4.   public $title;
  5.   public $producerMainName;
  6.   public $producerFirstName;
  7.   public $price;
  8.   function __construct(  $title, $firstName,
  9.               $mainName, $price ) {
  10.     $this->title       = $title;
  11.     $this->producerFirstName = $firstName;
  12.     $this->producerMainName = $mainName;
  13.     $this->price       = $price;
  14.   }
  15.   function getProducer() {
  16.     return "{$this->producerFirstName}".
  17.         " {$this->producerMainName}";
  18.   }
  19.   function getSummaryLine() {
  20.     $base = "{$this->title} ( {$this->producerMainName}, ";
  21.     $base .= "{$this->producerFirstName} )";
  22.     return $base;
  23.   }
  24. }
  25. class CdProduct extends ShopProduct {
  26.   public $playLength;
  27.   function __construct(  $title, $firstName,
  28.               $mainName, $price, $playLength ) {
  29.     parent::__construct(  $title, $firstName,
  30.                 $mainName, $price );
  31.     $this->playLength = $playLength;
  32.   }
  33.   function getPlayLength() {
  34.     return $this->playLength;
  35.   }
  36.   function getSummaryLine() {
  37.     $base = parent::getSummaryLine();
  38.     $base .= ": playing time - {$this->playLength}";
  39.     return $base;
  40.   }
  41. }
  42. class BookProduct extends ShopProduct {
  43.   public $numPages;
  44.   function __construct(  $title, $firstName,
  45.               $mainName, $price, $numPages ) {
  46.     parent::__construct(  $title, $firstName,
  47.                 $mainName, $price );
  48.     $this->numPages = $numPages;
  49.   }
  50.   function getNumberOfPages() {
  51.     return $this->numPages;
  52.   }
  53.   function getSummaryLine() {
  54.     $base = parent::getSummaryLine();
  55.     $base .= ": page count - {$this->numPages}";
  56.     return $base;
  57.   }
  58. }
  59. $product1 = new CdProduct("cd1", "bob", "bobbleson", 4, 50 );
  60. print $product1->getSummaryLine();
  61. print "\n";
  62. $product2 = new BookProduct("book1", "harry", "harrelson", 4, 30 );
  63. print $product2->getSummaryLine();
  64. print "\n";
  65. ?>

PHP编程输出：

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

PHP编程点评：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.

PHP编程继续添加一些有意思的内容

  1. PHP编程
  2. <?php
  3. class ShopProduct {
  4.   private $title;
  5.   private $discount = 0;
  6.   private $producerMainName;
  7.   private $producerFirstName;
  8.   protected $price;
  9.   function __construct(  $title, $firstName,
  10.               $mainName, $price ) {
  11.     $this->title       = $title;
  12.     $this->producerFirstName = $firstName;
  13.     $this->producerMainName = $mainName;
  14.     $this->price       = $price;
  15.   }
  16.   function setDiscount( $num ) {
  17.     $this->discount=$num;
  18.   }
  19.   function getPrice() {
  20.     return ($this->price - $this->discount);
  21.   }
  22.   function getProducer() {
  23.     return "{$this->producerFirstName}".
  24.         " {$this->producerMainName}";
  25.   }
  26.   function getSummaryLine() {
  27.     $base = "{$this->title} ( {$this->producerMainName}, ";
  28.     $base .= "{$this->producerFirstName} )";
  29.     return $base;
  30.   }
  31. }
  32. class CdProduct extends ShopProduct {
  33.   public $playLength;
  34.   function __construct(  $title, $firstName,
  35.               $mainName, $price, $playLength ) {
  36.     parent::__construct(  $title, $firstName,
  37.                 $mainName, $price );
  38.     $this->playLength = $playLength;
  39.   }
  40.   function getPlayLength() {
  41.     return $this->playLength;
  42.   }
  43.   function getSummaryLine() {
  44.     $base = parent::getSummaryLine();
  45.     $base .= ": playing time - {$this->playLength}";
  46.     return $base;
  47.   }
  48. }
  49. class BookProduct extends ShopProduct {
  50.   public $numPages;
  51.   function __construct(  $title, $firstName,
  52.               $mainName, $price, $numPages ) {
  53.     parent::__construct(  $title, $firstName,
  54.                 $mainName, $price );
  55.     $this->numPages = $numPages;
  56.   }
  57.   function getPrice() {
  58.     return $this->price;
  59.   }
  60.   function getNumberOfPages() {
  61.     return $this->numPages;
  62.   }
  63.   function getSummaryLine() {
  64.     $base = parent::getSummaryLine();
  65.     $base .= ": page count - {$this->numPages}";
  66.     return $base;
  67.   }
  68. }
  69. $product1 = new CdProduct("cd1", "bob", "bobbleson", 4, 50 );
  70. $product1->setDiscount( 3 );
  71. print $product1->getSummaryLine();
  72. print "\n";
  73. print "price: {$product1->getPrice()}\n";
  74. $product2 = new BookProduct("book1", "harry", "harrelson", 4, 30 );
  75. $product2->setDiscount( 3 ); // 折扣对book无效
  76. print $product2->getSummaryLine();
  77. print "\n";
  78. print "price: {$product2->getPrice()}\n";
  79. ?>

PHP编程输出：

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

PHP编程点评: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编程私有化属性,通过方法来设置与获取

  1. PHP编程
  2. <?php
  3. class ShopProduct {
  4.   // 私有化属性,通过方法来设置与获取
  5.   private $title;
  6.   private $producerMainName;
  7.   private $producerFirstName;
  8.   protected $price;
  9.   private $discount = 0;
  10.   public function __construct(  $title, $firstName,
  11.               $mainName, $price ) {
  12.     $this->title       = $title;
  13.     $this->producerFirstName = $firstName;
  14.     $this->producerMainName = $mainName;
  15.     $this->price       = $price;
  16.   }
  17.   public function getProducerFirstName() {
  18.     return $this->producerFirstName;
  19.   }
  20.   public function getProducerMainName() {
  21.     return $this->producerMainName;
  22.   }
  23.   public function setDiscount( $num ) {
  24.     $this->discount=$num;
  25.   }
  26.   public function getDiscount() {
  27.     return $this->discount;
  28.   }
  29.   public function getTitle() {
  30.     return $this->title;
  31.   }
  32.   public function getPrice() {
  33.     return ($this->price - $this->discount);
  34.   }
  35.   public function getProducer() {
  36.     return "{$this->producerFirstName}".
  37.         " {$this->producerMainName}";
  38.   }
  39.   public function getSummaryLine() {
  40.     $base = "{$this->title} ( {$this->producerMainName}, ";
  41.     $base .= "{$this->producerFirstName} )";
  42.     return $base;
  43.   }
  44. }
  45. class CdProduct extends ShopProduct {
  46.   private $playLength = 0;
  47.   public function __construct(  $title, $firstName,
  48.               $mainName, $price, $playLength ) {
  49.     parent::__construct(  $title, $firstName,
  50.                 $mainName, $price );
  51.     $this->playLength = $playLength;
  52.   }
  53.   public function getPlayLength() {
  54.     return $this->playLength;
  55.   }
  56.   public function getSummaryLine() {
  57.     $base = parent::getSummaryLine();
  58.     $base .= ": playing time - {$this->playLength}";
  59.     return $base;
  60.   }
  61. }
  62. class BookProduct extends ShopProduct {
  63.   private $numPages = 0;
  64.   public function __construct(  $title, $firstName,
  65.               $mainName, $price, $numPages ) {
  66.     parent::__construct(  $title, $firstName,
  67.                 $mainName, $price );
  68.     $this->numPages = $numPages;
  69.   }
  70.   public function getNumberOfPages() {
  71.     return $this->numPages;
  72.   }
  73.   public function getSummaryLine() {
  74.     $base = parent::getSummaryLine();
  75.     $base .= ": page count - {$this->numPages}";
  76.     return $base;
  77.   }
  78.   public function getPrice() {
  79.     return $this->price;
  80.   }
  81. }
  82. $product1 = new CdProduct("cd1", "bob", "bobbleson", 4, 50 );
  83. print $product1->getSummaryLine()."\n";
  84. $product2 = new BookProduct("book1", "harry", "harrelson", 4, 30 );
  85. print $product2->getSummaryLine()."\n";
  86. ?>

PHP编程输出：

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

PHP编程点评：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编程更多关于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》

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