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

<?phpclass 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

<?phpclass 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();