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

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									<?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();