PHP对象、模式与实践之高级特性分析

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

<?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();