php中的观察者模式简单实例

class DemoSubject implements SplSubject{
??? private $observers,$value;
?
??? public function __construct(){
??????? $this->observers = array();
??? }
?
??? public function attach(SplObserver $observer){
??????? $this->observers[] = $observer;
??? }
?
??? public function detach(SplObserver $observer){
??????? if($idx = array_search($observer,$this->observers,true)){
??????????? unset($this->observers[$idx]);
??????? }
??? }
?
??? public function notify(){
??????? foreach($this->observers as $observer){
??????????? $observer->update($this);
??????? }
??? }
?
??? public function setValue($value){
??????? $this->value = $value;
??????? $this->notify();
??? }
?
??? public function getValue(){
??????? return $this->value;
??? }
}
?
class DemoObserver implements SplObserver{
??? public function update(SplSubject $subject){
??????? echo 'The new value is '. $subject->getValue();
??? }
}
?
$subject = new DemoSubject();
$observer = new DemoObserver();
$subject->attach($observer);
$subject->setValue(5);