<?php
 /**
  * php设计模式 单例模式
  */
 class Fruit{
  private static $instanceMap = array();

  //protected getter for singleton instances
  protected static function getSingleton($className){
   //保证单例模式 并且不能从控制器实例化和克隆
   if (!isset(self::$instanceMap[$className])) {
    $object = new $className;
    //Make sure this object inherit from Singleton
    if ($object instanceof Fruit) {
     self::$instanceMap[$className] = $object;
     var_dump($object);
    } else {
     throw SingletonException("Class '$className' do not inherit from Singleton!");
    }
   }
   return self::$instanceMap[$className];
  }

  //protected constructor to prevent outside instantiation
  protected function __construct(){}

  //denie cloning of singleton objects
  public final function __clone(){
   trigger_error('It is impossible to clone singleton', E_USER_ERROR);
  }
 }

 class Apple extends Fruit{
  protected $rndId;

  public function __construct(){
   $this->rndId = rand();
  }

  public function whatAmI(){
   echo 'I am a Apple(' . $this->rndId . ')<br />';
  }

  public static function getInstance(){
   //echo get_class();
   return Fruit::getSingleton(get_class());
  }
 }

 class GreenApple extends Apple{
  public function whatAmI(){
   echo 'I am a GreenApple(' . $this->rndId . ')<br />';
  }

  public static function getInstance(){
   return Fruit::getSingleton(get_class());
  }
 }

 $apple1 = Apple::getInstance();
 //var_dump($apple1);
 $apple2 = GreenApple::getInstance();
 $apple1->whatAmI();// should echo 'I am a Apple(some number)
 $apple2->whatAmI();// should echo 'I am a GreenApple(some number)
 $apple1 = Apple::getInstance();
 $apple2 = GreenApple::getInstance();
 //保证单例模式
 $apple1->whatAmI();// should echo 'I am a Apple(same number as above)
 $apple2->whatAmI();// should echo 'I am a GreenApple(same number as above)
 // $a = clone $apple1;// this should fail
 // $b = clone $apple2;// this should fail