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1.php与对象
知识点：
a.关于引用赋值
other = &other = &my_obj;
//按照引用复制，指向相同对象。 例子：";//１$other = &$my_obj;echo $other."";//1$my_obj = 2;echo $other;//2//按照引用复制，指向相同对象。
2.类与对象
知识点
a.类是对象的模板，对象是类实现的实例
变量函数对应类中的属性和方法。
和函数不同的是，方法必须在类体中声明。
$this是伪变量，可以将类指向一个对象实例。
b.一个类实例
title = $title; $this->producerFirstName = $firstName; $this->producerMainName = $mainName; $this->price = $price; } function getProducer(){ return $this->producerFirstName." ".$this->producerMainName; }}$product1 = new ShopProduct("My pro","Willa","Tom",5.99);print "author:{ $product1->getProducer()}\n"; 输出：
author:Willa Tom
一个更复杂的例子
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; 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 getnumPages(){ 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; }}class ShopProduct{ public $title; public $producerMainName; public $producerFirstName; public $price = 0; function __construct($title,$firstName,$mainName,$price){ $this->title = $title; $this->producerFirstName = $firstName; $this->producerMainName = $mainName; $this->price = $price; } function getSummaryLine(){ $base = "{ $this->title}({ $this->producerMainName},"; $base .= "{ $this->producerFirstName})"; return $base; } function getProducer(){ return $this->producerFirstName." ".$this->producerMainName; }}$product1 = new ShopProduct("My pro","Willa","Tom",5.99);print "author:{ $product1->getProducer()}";$product2 = new CdProduct("My pro","Willa","Tom",5.99,1);print "PlayLength:{ $product2->getPlayLength()}";$product3 = new BookProduct("My pro","Willa","Tom",5.99,10);print "numPages:{ $product3->getnumPages()}"; 结果：
author:Willa Tom
PlayLength:1 numPages:10点评：这三个类写在同一个文件下面，说明php支持一个文件包含多个类。只是这样有点不太好，最好单独一个文件，把他们引入进来，然后创建对象，使用。
这三个类还有一个缺点就是，代码重复了，每个类中都有getSummaryLine()方法，和getProducer()方法。这样就冗余了，这个时候怎么办呢？
如果类之间有一定的继承关系，可以用继承这种机制，当然也不要继承很多层次，那样太深了也不好。
适当的继承能够让类更简洁，更利索！
下面是继承的案例：
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(){ return $this->playLength; } function getSummaryLine(){ $base = "{ $this->title}({ $this->producerMainName},"; $base .= "{ $this->producerFirstName})"; $base .= ":playing time { $this->playLength}"; return $base; }}class BookProduct extends ShopProduct{ function getnumPages(){ return $this->numPages; } function getSummaryLine(){ $base = "{ $this->title}({ $this->producerMainName},"; $base .= "{ $this->producerFirstName})"; $base .= ":page count { $this->numPages}"; return $base; }}$product1 = new ShopProduct("My pro","Willa","Tom",5.99);print "SummaryLine:{ $product1->getSummaryLine()}";$product2 = new CdProduct("My pro","Willa","Tom",5.99,null,5);print "SummaryLine:{ $product2->getSummaryLine()}";$product3 = new BookProduct("My pro","Willa","Tom",5.99,10,null);print "SummaryLine:{ $product3->getSummaryLine()}"; 结果：
SummaryLine:My pro(Tom,Willa)
SummaryLine:My pro(Tom,Willa):playing time 5 SummaryLine:My pro(Tom,Willa):page count 10点评：子类继承父类的属性和构造行数，以及一些基本的函数。
继承之后，可以覆盖父类的函数，也可以新建自己的函数。继承可以避免类内容的重复，代码的重复。
继续改造，子类中也有自己的构造方法。
在子类中定义构造方法时，需要传递参数给父类的构造方法，否则你得到的可能是一个构造不完整的对象。 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);//继承父类的构造函数 $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; }}class BookProduct extends ShopProduct{ public $numPages; function __construct($title,$firstName,$mainName,$price,$numPages){ parent::__construct($title,$firstName,$mainName,$price); $this->numPages = $numPages; } function getnumPages(){ return $this->numPages; } function getSummaryLine(){ $base = "{ $this->title}({ $this->producerMainName},"; $base .= "{ $this->producerFirstName})"; $base .= ":page count { $this->numPages}"; return $base; }}$product1 = new ShopProduct("My pro","Willa","Tom",5.99);print "SummaryLine:{ $product1->getSummaryLine()}";$product2 = new CdProduct("My pro","Willa","Tom",5.99,5);print "SummaryLine:{ $product2->getSummaryLine()}";$product3 = new BookProduct("My pro","Willa","Tom",5.99,10);print "SummaryLine:{ $product3->getSummaryLine()}"; 结果同上一个效果一点，这里面每个子类都有自己的构造方法了，同时继承了父类中的构造方法。这样就保证了子类的灵活性。不完全受制于父类。
进一步添加访问权限设置，
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); } function getProducer(){ return $this->producerFirstName." ".$this->producerMainName; } function getSummaryLine(){ $base = "$this->title({ $this->producerMainName},"; $base .= "{ $this->producerFirstName})"; return $base; }}class CdProduct extends ShopProduct{ private $playLength; function __construct($title,$firstName,$mainName,$price,$playLength){ parent::__construct($title,$firstName,$mainName,$price);//继承父类的构造函数 $this->playLength = $playLength; } function getPlayLength(){ return $this->playLength; } function getSummaryLine(){ $base = parent::getSummaryLine(); $base .= ":playing time { $this->playLength}"; return $base; }}class BookProduct extends ShopProduct{ private $numPages = 0; function __construct($title,$firstName,$mainName,$price,$numPages){ parent::__construct($title,$firstName,$mainName,$price); $this->numPages = $numPages; } function getnumPages(){ return $this->numPages; } function getSummaryLine(){ $base = parent::getSummaryLine(); $base .= ":page count { $this->numPages}"; return $base; }}$product1 = new ShopProduct("My pro","Willa","Tom",5.99);print "SummaryLine:{ $product1->getSummaryLine()}";$product2 = new CdProduct("My pro","Willa","Tom",5.99,5);print "SummaryLine:{ $product2->getSummaryLine()}";$product3 = new BookProduct("My pro","Willa","Tom",5.99,10);print "SummaryLine:{ $product3->getSummaryLine()}"; 点评：一般属性设置为私有的，只能通过方法来设置和获取，这样能保证安全性。
本文转自TBHacker博客园博客，原文链接http://www.cnblogs.com/jiqing9006/p/3178339.html，如需转载请自行联系原作者