<?php /*** Singleton of Database*/class Database{  // We need a static private variable to store a Database instance.  privatestatic $instance;   // Mark as private to prevent it from being instanced.  privatefunction__construct()  {    // Do nothing.  }   privatefunction__clone()   {    // Do nothing.  }   publicstatic functiongetInstance()   {    if (!(self::$instanceinstanceofself)) {      self::$instance = newself();    }     returnself::$instance;  }} $a =Database::getInstance();$b =Database::getInstance(); // truevar_dump($a === $b); 

 <?php interfaceInterfaceShape { functiongetArea(); functiongetCircumference();} /*** 矩形*/class Rectangle implementsInterfaceShape{  private $width;  private $height;    publicfunction__construct($width, $height)  {    $this->width = $width;    $this->height = $height;  }   publicfunctiongetArea()   {    return $this->width* $this->height;  }   publicfunctiongetCircumference()  {    return 2 * $this->width + 2 * $this->height;  }} /*** 圓形*/class Circle implementsInterfaceShape{  private $radius;   function__construct($radius)  {    $this->radius = $radius;  }    publicfunctiongetArea()   {    return M_PI * pow($this->radius, 2);  }   publicfunctiongetCircumference()  {    return 2 * M_PI * $this->radius;  }} /*** 形狀工廠類*/class FactoryShape {   publicstatic functioncreate()  {    switch (func_num_args()) {      case1:      return newCircle(func_get_arg(0));      case2:      return newRectangle(func_get_arg(0), func_get_arg(1));      default:        # code...        break;    }  } } $rect =FactoryShape::create(5, 5);// object(Rectangle)#1 (2) { ["width":"Rectangle":private]=> int(5) ["height":"Rectangle":private]=> int(5) }var_dump($rect);echo "<br>"; // object(Circle)#2 (1) { ["radius":"Circle":private]=> int(4) }$circle =FactoryShape::create(4);var_dump($circle); 

 <?php /*觀察者接口*/interfaceInterfaceObserver{  functiononListen($sender, $args);  functiongetObserverName();} // 可被觀察者接口interfaceInterfaceObservable{  functionaddObserver($observer);  functionremoveObserver($observer_name);} // 觀察者抽象類abstractclass Observer implementsInterfaceObserver{  protected $observer_name;   functiongetObserverName()   {    return $this->observer_name;  }   functiononListen($sender, $args)  {   }} // 可被觀察類abstractclass Observable implementsInterfaceObservable {  protected $observers = array();   publicfunctionaddObserver($observer)   {    if ($observerinstanceofInterfaceObserver)     {      $this->observers[] = $observer;    }  }   publicfunctionremoveObserver($observer_name)   {    foreach ($this->observersas $index => $observer)     {      if ($observer->getObserverName() === $observer_name)       {        array_splice($this->observers, $index, 1);        return;      }    }  }} // 模擬一個可以被觀察的類class A extendsObservable {  publicfunctionaddListener($listener)   {    foreach ($this->observersas $observer)     {      $observer->onListen($this, $listener);    }  }} // 模擬一個觀察者類class B extendsObserver {  protected $observer_name = 'B';   publicfunctiononListen($sender, $args)   {    var_dump($sender);    echo "<br>";    var_dump($args);    echo "<br>";  }} // 模擬另外一個觀察者類class C extendsObserver {  protected $observer_name = 'C';   publicfunctiononListen($sender, $args)   {    var_dump($sender);    echo "<br>";    var_dump($args);    echo "<br>";  }} $a = new A();// 注入觀察者$a->addObserver(new B());$a->addObserver(new C()); // 可以看到觀察到的信息$a->addListener('D'); // 移除觀察者$a->removeObserver('B'); // 打印的信息：// object(A)#1 (1) { ["observers":protected]=> array(2) { [0]=> object(B)#2 (1) { ["observer_name":protected]=> string(1) "B" } [1]=> object(C)#3 (1) { ["observer_name":protected]=> string(1) "C" } } }// string(1) "D"// object(A)#1 (1) { ["observers":protected]=> array(2) { [0]=> object(B)#2 (1) { ["observer_name":protected]=> string(1) "B" } [1]=> object(C)#3 (1) { ["observer_name":protected]=> string(1) "C" } } }// string(1) "D"