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：
继承
先看两个类
<?php
classCdProduct{
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;
}
functiongetPlayLength(){
return$this->playLength;
}
functiongetSummaryLine(){
$base="{$this->title}({$this->producerMainName},";
$base.="{$this->producerFirstName})";
$base.=":playingtime-{$this->playLength}";
return$base;
}
functiongetProducer(){
return"{$this->producerFirstName}".
"{$this->producerMainName}";
}
}
classBookProduct{
public$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;
}
functiongetNumberOfPages(){
return$this->numPages;
}
functiongetSummaryLine(){
$base="{$this->title}({$this->producerMainName},";
$base.="{$this->producerFirstName})";
$base.=":pagecount-{$this->numPages}";
return$base;
}
functiongetProducer(){
return"{$this->producerFirstName}".
"{$this->producerMainName}";
}
}
$product1=newCdProduct("cd1","bob","bobbleson",4,50);
print$product1->getSummaryLine();
print"\n";
$product2=newBookProduct("book1","harry","harrelson",4,30);
print$product2->getSummaryLine();
print"\n";
?>
输出：
cd1(bobbleson,bob):playingtime-50
book1(harrelson,harry):pagecount-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。
采用继承来处理
<?php
classShopProduct{
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;
}
functiongetProducer(){
return"{$this->producerFirstName}".
"{$this->producerMainName}";
}
functiongetSummaryLine(){
$base="$this->title({$this->producerMainName},";
$base.="{$this->producerFirstName})";
return$base;
}
}
classCdProductextendsShopProduct{
functiongetPlayLength(){//增加属于自己的方法
return$this->playLength;
}
functiongetSummaryLine(){//改造了父类的方法
$base="{$this->title}({$this->producerMainName},";
$base.="{$this->producerFirstName})";
$base.=":playingtime-{$this->playLength}";
return$base;
}
}
classBookProductextendsShopProduct{
functiongetNumberOfPages(){
return$this->numPages;
}
functiongetSummaryLine(){
$base="{$this->title}({$this->producerMainName},";
$base.="{$this->producerFirstName})";
$base.=":pagecount-{$this->numPages}";
return$base;
}
}
$product1=newCdProduct("cd1","bob","bobbleson",4,null,50);
print$product1->getSummaryLine();
print"\n";
$product2=newBookProduct("book1","harry","harrelson",4,30);
print$product2->getSummaryLine();
print"\n";
?>
输出：
cd1(bobbleson,bob):playingtime-50
book1(harrelson,harry):pagecount-30
点评：继承处理很好的解决了差异性，相通性问题。
进一步优化处理
<?php
classShopProduct{
//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;
}
functiongetProducer(){
return"{$this->producerFirstName}".
"{$this->producerMainName}";
}
functiongetSummaryLine(){
$base="{$this->title}({$this->producerMainName},";
$base.="{$this->producerFirstName})";
return$base;
}
}
classCdProductextendsShopProduct{
//抽离出属于自己特有的属性
public$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
}
functiongetPlayLength(){
return$this->playLength;
}
functiongetSummaryLine(){
$base="{$this->title}({$this->producerMainName},";
$base.="{$this->producerFirstName})";
$base.=":playingtime-{$this->playLength}";
return$base;
}
}
classBookProductextendsShopProduct{
public$numPages;
function__construct($title,$firstName,
$mainName,$price,$numPages){
parent::__construct($title,$firstName,
$mainName,$price);
$this->numPages=$numPages;
}
functiongetNumberOfPages(){
return$this->numPages;
}
functiongetSummaryLine(){
$base="$this->title($this->producerMainName,";
$base.="$this->producerFirstName)";
$base.=":pagecount-$this->numPages";
return$base;
}
}
$product1=newCdProduct("cd1","bob","bobbleson",4,50);
print$product1->getSummaryLine();
print"\n";
$product2=newBookProduct("book1","harry","harrelson",4,30);
print$product2->getSummaryLine();
print"\n";
?>
输出：
cd1(bobbleson,bob):playingtime-50
book1(harrelson,harry):pagecount-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。
进一步继承父类的方法
<?php
classShopProduct{
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;
}
functiongetProducer(){
return"{$this->producerFirstName}".
"{$this->producerMainName}";
}
functiongetSummaryLine(){
$base="{$this->title}({$this->producerMainName},";
$base.="{$this->producerFirstName})";
return$base;
}
}
classCdProductextendsShopProduct{
public$playLength;
function__construct($title,$firstName,
$mainName,$price,$playLength){
parent::__construct($title,$firstName,
$mainName,$price);
$this->playLength=$playLength;
}
functiongetPlayLength(){
return$this->playLength;
}
functiongetSummaryLine(){
$base=parent::getSummaryLine();
$base.=":playingtime-{$this->playLength}";
return$base;
}
}
classBookProductextendsShopProduct{
public$numPages;
function__construct($title,$firstName,
$mainName,$price,$numPages){
parent::__construct($title,$firstName,
$mainName,$price);
$this->numPages=$numPages;
}
functiongetNumberOfPages(){
return$this->numPages;
}
functiongetSummaryLine(){
$base=parent::getSummaryLine();
$base.=":pagecount-{$this->numPages}";
return$base;
}
}
$product1=newCdProduct("cd1","bob","bobbleson",4,50);
print$product1->getSummaryLine();
print"\n";
$product2=newBookProduct("book1","harry","harrelson",4,30);
print$product2->getSummaryLine();
print"\n";
?>
输出：
cd1(bobbleson,bob):playingtime-50
book1(harrelson,harry):pagecount-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。
继续添加一些有意思的内容
<?php
classShopProduct{
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;
}
functionsetDiscount($num){
$this->discount=$num;
}
functiongetPrice(){
return($this->price-$this->discount);
}
functiongetProducer(){
return"{$this->producerFirstName}".
"{$this->producerMainName}";
}
functiongetSummaryLine(){
$base="{$this->title}({$this->producerMainName},";
$base.="{$this->producerFirstName})";
return$base;
}
}
classCdProductextendsShopProduct{
public$playLength;
function__construct($title,$firstName,
$mainName,$price,$playLength){
parent::__construct($title,$firstName,
$mainName,$price);
$this->playLength=$playLength;
}
functiongetPlayLength(){
return$this->playLength;
}
functiongetSummaryLine(){
$base=parent::getSummaryLine();
$base.=":playingtime-{$this->playLength}";
return$base;
}
}
classBookProductextendsShopProduct{
public$numPages;
function__construct($title,$firstName,
$mainName,$price,$numPages){
parent::__construct($title,$firstName,
$mainName,$price);
$this->numPages=$numPages;
}
functiongetPrice(){
return$this->price;
}
functiongetNumberOfPages(){
return$this->numPages;
}
functiongetSummaryLine(){
$base=parent::getSummaryLine();
$base.=":pagecount-{$this->numPages}";
return$base;
}
}
$product1=newCdProduct("cd1","bob","bobbleson",4,50);
$product1->setDiscount(3);
print$product1->getSummaryLine();
print"\n";
print"price:{$product1->getPrice()}\n";
$product2=newBookProduct("book1","harry","harrelson",4,30);
$product2->setDiscount(3);//折扣对book无效
print$product2->getSummaryLine();
print"\n";
print"price:{$product2->getPrice()}\n";
?>
输出：
cd1(bobbleson,bob):playingtime-50
price:1
book1(harrelson,harry):pagecount-30
price:4
点评:父类添加了折扣，book继承之后，修改了getPrice方法，所以折扣对book无效。
私有化属性，通过方法来设置与获取
<?php
classShopProduct{
//私有化属性，通过方法来设置与获取
private$title;
private$producerMainName;
private$producerFirstName;
protected$price;
private$discount=0;
publicfunction__construct($title,$firstName,
$mainName,$price){
$this->title=$title;
$this->producerFirstName=$firstName;
$this->producerMainName=$mainName;
$this->price=$price;
}
publicfunctiongetProducerFirstName(){
return$this->producerFirstName;
}
publicfunctiongetProducerMainName(){
return$this->producerMainName;
}
publicfunctionsetDiscount($num){
$this->discount=$num;
}
publicfunctiongetDiscount(){
return$this->discount;
}
publicfunctiongetTitle(){
return$this->title;
}
publicfunctiongetPrice(){
return($this->price-$this->discount);
}
publicfunctiongetProducer(){
return"{$this->producerFirstName}".
"{$this->producerMainName}";
}
publicfunctiongetSummaryLine(){
$base="{$this->title}({$this->producerMainName},";
$base.="{$this->producerFirstName})";
return$base;
}
}
classCdProductextendsShopProduct{
private$playLength=0;
publicfunction__construct($title,$firstName,
$mainName,$price,$playLength){
parent::__construct($title,$firstName,
$mainName,$price);
$this->playLength=$playLength;
}
publicfunctiongetPlayLength(){
return$this->playLength;
}
publicfunctiongetSummaryLine(){
$base=parent::getSummaryLine();
$base.=":playingtime-{$this->playLength}";
return$base;
}
}
classBookProductextendsShopProduct{
private$numPages=0;
publicfunction__construct($title,$firstName,
$mainName,$price,$numPages){
parent::__construct($title,$firstName,
$mainName,$price);
$this->numPages=$numPages;
}
publicfunctiongetNumberOfPages(){
return$this->numPages;
}
publicfunctiongetSummaryLine(){
$base=parent::getSummaryLine();
$base.=":pagecount-{$this->numPages}";
return$base;
}
publicfunctiongetPrice(){
return$this->price;
}
}
$product1=newCdProduct("cd1","bob","bobbleson",4,50);
print$product1->getSummaryLine()."\n";
$product2=newBookProduct("book1","harry","harrelson",4,30);
print$product2->getSummaryLine()."\n";
?>
输出：
cd1(bobbleson,bob):playingtime-50
book1(harrelson,harry):pagecount-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。
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