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這篇文章給大家分享的是有關PHP中如何實現繼承的內容。小編覺得挺實用的，因此分享給大家做個參考，一起跟隨小編過來看看吧。
具體如下：
繼承
先看兩個類
<?php
class CdProduct {
public $playLength; // 播放時間
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; // 看的頁數
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";
?>輸出：
cd1 ( bobbleson, bob ): playing time - 50
book1 ( harrelson, harry ): page count - 30
點評：這兩個類，代碼重復性太高，有相同性，也有差異性。不如用繼承來簡化處理。
采用繼承來處理
<?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() { // 增加屬于自己的方法
return $this->playLength;
}
function getSummaryLine() { // 改造了父類的方法
$base = "{$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";
?>輸出：
cd1 ( bobbleson, bob ): playing time - 50
book1 ( harrelson, harry ): page count - 30
點評：繼承處理很好的解決了差異性，相通性問題。
進一步優化處理
<?php
class ShopProduct {
// 抽離出共有屬性
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 {
// 抽離出屬于自己特有的屬性
public $playLength;
function __construct( $title, $firstName,
$mainName, $price, $playLength ) {
parent::__construct( $title, $firstName,
$mainName, $price ); // 繼承父類的構造函數
$this->playLength = $playLength; // 處理自己專有的屬性
}
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";
?>輸出：
cd1 ( bobbleson, bob ): playing time - 50
book1 ( harrelson, harry ): page count - 30
點評：這里把共有屬性在父類中，其他個性屬性放在自己的類中處理。并設置自己的構造方法，繼承父類的構造方法。
進一步繼承父類的方法
<?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";
?>輸出：
cd1 ( bobbleson, bob ): playing time - 50
book1 ( harrelson, harry ): page count - 30
點評：同樣的結果，可以優化優化再優化。這里繼承父類的方法。parent::getSummaryLine()。不過這個用的比較少。
繼續添加一些有意思的內容
<?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 ); // 折扣對book無效
print $product2->getSummaryLine();
print "\n";
print "price: {$product2->getPrice()}\n";
?>輸出：
cd1 ( bobbleson, bob ): playing time - 50
price: 1
book1 ( harrelson, harry ): page count - 30
price: 4
點評:父類添加了折扣，book繼承之后，修改了getPrice方法，所以折扣對book無效。
私有化屬性，通過方法來設置與獲取
<?php
class ShopProduct {
// 私有化屬性，通過方法來設置與獲取
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";
?>輸出：
cd1 ( bobbleson, bob ): playing time - 50
book1 ( harrelson, harry ): page count - 30
感謝各位的閱讀！關于“PHP中如何實現繼承”這篇文章就分享到這里了，希望以上內容可以對大家有一定的幫助，讓大家可以學到更多知識，如果覺得文章不錯，可以把它分享出去讓更多的人看到吧！
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