這篇文章給大家分享的是有關(guān)PHP中如何實(shí)現(xiàn)繼承的內(nèi)容。小編覺(jué)得挺實(shí)用的,因此分享給大家做個(gè)參考,一起跟隨小編過(guò)來(lái)看看吧。
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繼承
先看兩個(gè)類(lèi)
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(yè)數(shù) 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(diǎn)評(píng):這兩個(gè)類(lèi),代碼重復(fù)性太高,有相同性,也有差異性。不如用繼承來(lái)簡(jiǎn)化處理。
采用繼承來(lái)處理
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(lèi)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(diǎn)評(píng):繼承處理很好的解決了差異性,相通性問(wèn)題。
進(jìn)一步優(yōu)化處理
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(lèi)的構(gòu)造函數(shù) $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(diǎn)評(píng):這里把共有屬性在父類(lèi)中,其他個(gè)性屬性放在自己的類(lèi)中處理。并設(shè)置自己的構(gòu)造方法,繼承父類(lèi)的構(gòu)造方法。
進(jìn)一步繼承父類(lèi)的方法
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(diǎn)評(píng):同樣的結(jié)果,可以優(yōu)化優(yōu)化再優(yōu)化。這里繼承父類(lèi)的方法。parent::getSummaryLine()。不過(guò)這個(gè)用的比較少。
繼續(xù)添加一些有意思的內(nèi)容
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(duì)book無(wú)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(diǎn)評(píng):父類(lèi)添加了折扣,book繼承之后,修改了getPrice方法,所以折扣對(duì)book無(wú)效。
私有化屬性,通過(guò)方法來(lái)設(shè)置與獲取
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
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