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); 复制代码