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PHP面向对象继承用法详解(优化与减少代码重复)

  • 时间：2021-06-15 13:42 编辑： 来源： 阅读：
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摘要：PHP面向对象继承用法详解(优化与减少代码重复)
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： [b]继承[/b] [b]先看两个类[/b] 
<?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。 [b]采用继承来处理[/b] 
<?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。 [b]进一步优化处理[/b] 
<?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。 [b]进一步继承父类的方法[/b] 
<?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。 [b]继续添加一些有意思的内容[/b] 
<?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。 [b]私有化属性，通过方法来设置与获取[/b] 
<?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。 更多关于PHP相关内容感兴趣的读者可查看本站专题：《[url=http://www.1sucai.cn/Special/43.htm]php面向对象程序设计入门教程[/url]》、《[url=http://www.1sucai.cn/Special/348.htm]PHP基本语法入门教程[/url]》、《[url=http://www.1sucai.cn/Special/357.htm]PHP运算与运算符用法总结[/url]》、《[url=http://www.1sucai.cn/Special/495.htm]PHP网络编程技巧总结[/url]》、《[url=http://www.1sucai.cn/Special/623.htm]PHP数组(Array)操作技巧大全[/url]》、《[url=http://www.1sucai.cn/Special/47.htm]php字符串(string)用法总结[/url]》、《[url=http://www.1sucai.cn/Special/84.htm]php+mysql数据库操作入门教程[/url]》及《[url=http://www.1sucai.cn/Special/231.htm]php常见数据库操作技巧汇总[/url]》 希望本文所述对大家PHP程序设计有所帮助。
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