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原文链接：https://www.f2er.com/php/19566.html//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 . ')
';
}
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
