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php调用父类构造方法:使用parent调用父类的构造,用【::】引用一个类,代码为【parent::__construct($title,$firstName,$mainName,$price)】。

php如何调用父类构造方法?

php调用父类构造方法:

使用parent调用父类的构造方法

要引用一个类而不是对象的方法,可以使用 ::(两个冒号),而不是 ->

所以, parent::__construct() 为着调用父类的 __construct() 方法。

具体代码如下:

<?phpheader('Content-type:text/html;charset=utf-8');// 从这篇开始,类名首字母一律大写,规范写法class ShopProduct{    // 声明类public $title; // 声明属性public $producerMainName;public $producerFirstName;public $price;function __construct($title,$firstName,$mainName,$price){$this -> title = $title;    // 给属性 title 赋传进来的值$this -> producerFirstName= $firstName; $this -> producerMainName = $mainName; $this -> price= $price; }function getProducer(){    // 声明方法return "{$this -> producerFirstName }"."{$this -> producerMainName}";}function getSummaryLine(){$base = "{$this->title}( {$this->producerMainName},";$base .= "{$this->producerFirstName} )";return $base;}}class CdProduct extends ShopProduct {public $playLenth;function __construct($title,$firstName,$mainName,$price,$playLenth){parent::__construct($title,$firstName,$mainName,$price);$this -> playLenth= $playLenth;}function getPlayLength(){return $this -> playLength;}function getSummaryLine(){$base = "{$this->title}( {$this->producerMainName},";$base .= "{$this->producerFirstName} )";$base .= ":playing time - {$this->playLength} )";return $base;}}// 定义类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} )";$base .= ":page cont - {$this->numPages} )";return $base;}} ?>

每个子类都会在设置自己的属性前调用父类的构造方法。基类(父类)现在仅知道自己的数据,而我们也应该尽量避免告诉父类任何关于子类的信息,这是一条经验规则,大家想想如果某个子类的信息应该是”保密“的,结果父类知道它的信息,其它子类可以继承,这样子类的信息就不保密了。

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