/**

* 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 . ')
';

}

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 . ')
';

}

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