How to call the parent class constructor in php?-PHP Problem-php.cn

php calls the parent class constructor: use parent to call the parent class's constructor, use [::] to reference a class, the code is [parent::__construct($title,$firstName,$mainName,$price) 】.

How to call the parent class constructor in php?

php calls the parent class constructor:

Useparentto call the parent class constructor Method

To refer to a method of a class rather than an object, use::(two colons) instead of->.

So,parent::__construct()In order to call the__construct()method of the parent class.

The specific code is as follows:

 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; } } ?>

Copy after login

Each subclass will call the constructor of the parent class before setting its own properties. The base class (parent class) now only knows its own data, and we should try to avoid telling the parent class any information about the subclass. This is a rule of thumb. Think about it if the information of a certain subclass should be "confidential" , as a result, the parent class knows its information, and other subclasses can inherit it, so that the subclass's information is not kept confidential.

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