SplSubject::attach

i think that Observer pattern is always implemented as "static" to be called from any scope, for example:<?phpclass Observer {     //attach here the caller's scope     private static $stackTrace = array( );     public static function wasTriggeredOnce() {          //...if is not in the stack, then:          self::$stackTrace[] = max( debug_backtrace( ) );     }}class YourFramework {     public function launchPlatform() {          //could not let user to launch application twice!          Observer::wasTriggeredOnce();     }}//cause is staticObserver::hereIsnoNeedToInstantiateAgain(); ?>

The most obvious storage type for observers (stored in attach()) is array. In order to be able to detach attached objects, you should be able to identify it inside observer storage.I suggest you attach observers this way:$this->_observers[spl_object_hash($observer)] = $observer;so you can detach it later if you need:unset($this->_observers[spl_object_hash($observer)]);