/**
* Singleton of Database
*/
class Database
{
  // We need a static private variable to store a Database instance.
  privatestatic $instance;
 
  // Mark as private to prevent it from being instanced.
  private function__construct()
  {
    // Do nothing.
  }
 
  private function__clone() 
  {
    // Do nothing.
  }
 
  public static function getInstance() 
  {
    if (!(self::$instance instanceof self)) {
      self::$instance = new self();
    }
 
    return self::$instance;
  }
}
 
$a =Database::getInstance();
$b =Database::getInstance();
 
// true
var_dump($a === $b);

interface InterfaceShape { function getArea(); function getCircumference(); } /** * 矩形 */ class Rectangle implements InterfaceShape { private $width; private $height; public function __construct($width, $height) { $this->width = $width;
    $this->height = $height;
  }
 
  public function getArea() 
  {
    return $this->width* $this->height;
  }
 
  public function getCircumference()
  {
    return 2 * $this->width + 2 * $this->height;
  }
}
 
/**
* 圆形
*/
class Circle implements InterfaceShape
{
  private $radius;
 
  function __construct($radius)
  {
    $this->radius = $radius;
  }
 
 
  public function getArea() 
  {
    return M_PI * pow($this->radius, 2);
  }
 
  public function getCircumference()
  {
    return 2 * M_PI * $this->radius;
  }
}
 
/**
* 形状工厂类
*/
class FactoryShape 
{ 
  public static function create()
  {
    switch (func_num_args()) {
      case 1:
      return new Circle(func_get_arg(0));
      case 2:
      return new Rectangle(func_get_arg(0), func_get_arg(1));
      default:
        # code...
        break;
    }
  } 
}
 
$rect =FactoryShape::create(5, 5);
var_dump($rect->getArea());
echo "
";
 
$circle =FactoryShape::create(4);
var_dump($circle);

#===================定义观察者、被观察者接口============
/**
 * 
 * 观察者接口(通知接口)
 * 
 */
interface ITicketObserver //观察者接口
{
    function onBuyTicketOver($sender, $args); //得到通知后调用的方法
}
 
/**
 * 
 * 主题接口
 *
 */
interface ITicketObservable //被观察对象接口
{
    function addObserver($observer); //提供注册观察者方法
}
#====================主题类实现========================
/**
 * 
 * 主题类（购票）
 *
 */
class HipiaoBuy implements ITicketObservable { //实现主题接口（被观察者）
    private $_observers = array (); //通知数组（观察者）
    
 
    public function buyTicket($ticket) //购票核心类，处理购票流程
    {
       // TODO 购票逻辑
       //循环通知，调用其onBuyTicketOver实现不同业务逻辑
       foreach ( $this->_observers as $obs )
           $obs->onBuyTicketOver ( $this, $ticket ); //$this 可用来获取主题类句柄，在通知中使用
    }
    
    //添加通知
    public function addObserver($observer) //添加N个通知
    {
       $this->_observers [] = $observer;
    }
}
 
#=========================定义多个通知====================
//短信日志通知
class HipiaoMSM implements ITicketObserver {
    public function onBuyTicketOver($sender, $ticket) {
       echo (date ( 'Y-m-d H:i:s' ) . " 短信日志记录：购票成功:$ticket
");
    }
}
//文本日志通知
class HipiaoTxt implements ITicketObserver {
    public function onBuyTicketOver($sender, $ticket) {
       echo (date ( 'Y-m-d H:i:s' ) . " 文本日志记录：购票成功:$ticket
");
    }
}
//抵扣卷赠送通知
class HipiaoDiKou implements ITicketObserver {
    public function onBuyTicketOver($sender, $ticket) {
       echo (date ( 'Y-m-d H:i:s' ) . " 赠送抵扣卷：购票成功:$ticket 赠送10元抵扣卷1张。
");
    }
}
#============================用户购票====================
$buy = new HipiaoBuy ();
$buy->addObserver ( new HipiaoMSM () ); //根据不同业务逻辑加入各种通知
$buy->addObserver ( new HipiaoTxt () );
$buy->addObserver ( new HipiaoDiKou () );
//购票
$buy->buyTicket ( "一排一号" );
?>

//适配目标，规定的接口将被适配对象实现
interface IDatabase
{
  public function connect($host, $username, $password, $database);
  public function query($sql);
}
 
//适配器
class Mysql implements IDatabase
{
  protected $connect;
 
  public function connect($host, $username, $password, $database)
  {
    $connect = mysql_connect($host, $username, $password);
    mysql_select_db($database, $connect);
    $this->connect = $connect;
    //...
  }
 
  public function query($sql)
  {
    //...
  }
}
 
//适配器
class Postgresql implements IDatabase
{
  protected $connect;
 
  public function connect($host, $username, $password, $database)
  {
    $this->connect = pg_connect("host=$host dbname=$database user=$username password=$password");
    //...
  }
 
  public function query($sql)
  {
    //...
  }
}
 
 
//客户端使用
$client = new Postgresql();
$client->query($sql);