PHP对象、模式与实践之高级特性分析

本文实例讲述了PHP面向对象程序设计高级特性。分享给大家供大家参考，具体如下：高级特

本文实例讲述了PHP面向对象程序设计高级特性。分享给大家供大家参考，具体如下：

高级特性

包括：

1.静态方法和属性（通过类而不是对象来访问数据和功能） 2.抽象类和接口（设计，实现分离） 3.错误处理（异常） 4.Final类和方法（限制继承） 5.拦截器（自动委托） 6.析构方法（对象销毁前的清理工作） 7.克隆对象（创建对象的副本） 8.把对象解析成字符串

PS，学会从内存的角度看代码。想象计算机的微观世界。

静态方法的小例子

<?php
class StaticExample{
 static public $aNum = 10;
 static public function sayHello(){
 print "hello";
 }
}
print StaticExample::$aNum."<br/>";
StaticExample::sayHello();

tips:

1.静态方法不能访问类中的普通属性，因为那些属性属于一个对象，但可以访问静态属性。 2.我们不能再对象中调用静态方法，因此不能再静态方法中使用伪变量$this。

静态方法的大例子

<?php
class ShopProduct{
 private $title;
 private $producerMainName;
 private $producerFirstName;
 protected $price;
 private $discount = 0;
 private $id = 0;
 function __construct($title,$firstName,$mainName,$price){
 $this->title = $title;
 $this->producerFirstName = $firstName;
 $this->producerMainName = $mainName;
 $this->price = $price;
 }
 public function setID($id){
 $this->id = $id;
 }
 public static function getInstance($id,PDO $pdo){
 $query = "select * from products where id= '$id'";
 $stmt = $pdo->query($query);
 $row = $stmt->fetch();
 if(empty($row)){
 return null;
 }
 if($row['type'] == "book"){
 $product = new BookProduct($row['title'],
 $row['firstname'],
 $row['mainname'],
 $row['price'],
 $row['numpages']
 );
 }else if($row['type'] == "cd"){
 $product = new CdProduct($row['title'],
 $row['firstname'],
 $row['mainname'],
 $row['price'],
 $row['playLength']
 );
 }else{
 $product = new ShopProduct($row['title'],
 $row['firstname'],
 $row['mainname'],
 $row['price']
 );
 }
 $product->setId($row['id']);
 $product->setDiscount($row['discount']);
 return $product;
 }
 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;
 }
}
$dsn = "sqlite:C:/Users/Administrator/Desktop/shop.db";
$pdo = new PDO($dsn,null,null);
$pdo->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
$obj = ShopProduct::getInstance(1,$pdo);
echo $obj->getSummaryLine();