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

<?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();

更多关于php相关内容感兴趣的读者可查看本站专题：《php面向对象程序设计入门教程》、《php基本语法入门教程》、《php运算与运算符用法总结》、《php网络编程技巧总结》、《php数组(array)操作技巧大全》、《php字符串(string)用法总结》、《php+mysql数据库操作入门教程》及《php常见数据库操作技巧汇总》

希望本文所述对大家php程序设计有所帮助。