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  • SplSubject::attach()

    (PHP 5 >= 5.1.0, PHP 7)

    Attach an SplObserver

    说明

    abstractpublicSplSubject::attach(SplObserver$observer): void

    Attaches an SplObserver so that it can be notified of updates.

    Warning

    本函数还未编写文档,仅有参数列表。

    参数

    $observer

    The SplObserver to attach.

    返回值

    没有返回值。

    i think that Observer pattern is always implemented as "static" to be called from any scope, for example:
    <?php
    class 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 static
    Observer::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)]);