PHP hook, building hooks in your application

Introduction
One of the real challenges in building any type of framework, core or application is making it possible for the developers to hook into the business logic at specific points. Since PHP is not event based, nor it works with interrupts you have to come up an alternative.

The test case
Lets assume we are the main developers of a webshop framework. Programmers can use our framework to build complete webshops. Programmers can manage the orders that are placed on the webshop with the order class. The order class is part of our framework and we don’t want it to be extended by any programmer. However we don’t want to limit to programmers in their possibilities to hook into the orders process.

For example programmers should be able to send an email to the webshopowner if an order changes from one specific delivery status to another. This functionality is not part of the default behavior in our framework and is custom for the progammers webshop implementation.

Like said before, PHP doesn’t provide interrupts or real events so we need to come up with another way to implement hooks into our application. Lets take a look at the observer pattern.

Implementing the Observer pattern
The observer pattern is a design-pattern that describes a way for objects to be notified to specific state-changes in objects of the application.

For the first implementation we can use SPL. The SPL provides in two simple objects:

SPLSubject

attach (new observer to attach)
detach (existing observer to detach)
notify (notify all observers)

SPLObserver

update (Called from the subject (i.e. when it’s value has changed).

iOrderRef = $iOrderRef;
		
		// Get order information from the database or an other resources
		$this->iStatus = Order::STATUS_SHIPPED;
	}
	
	/**
	 * Attach an observer
	 * 
	 * @param SplObserver $oObserver 
	 * @return void
	 */
	public function attach(SplObserver $oObserver)
	{
		$sHash = spl_object_hash($oObserver);
		if (isset($this->aObservers[$sHash])) {
			throw new Exception('Observer is already attached');
		}

		$this->aObservers[$sHash] = $oObserver;
	}

	/**
	 * Detach observer
	 * 
	 * @param SplObserver $oObserver 
	 * @return void
	 */
	public function detach(SplObserver $oObserver)
	{
		$sHash = spl_object_hash($oObserver);
		if (!isset($this->aObservers[$sHash])) {
			throw new Exception('Observer not attached');
		}
		unset($this->aObservers[$sHash]);
	}

	/**
	 * Notify the attached observers
	 * 
	 * @param string $sEvent, name of the event
	 * @param mixed $mData, optional data that is not directly available for the observers
	 * @return void
	 */
	public function notify()
	{
		foreach ($this->aObservers as $oObserver) {
			try {
				$oObserver->update($this);
			} catch(Exception $e) {

			}
		}
	}

	/**
	 * Add an order
	 * 
	 * @param array $aOrder 
	 * @return void
	 */
	public function delete()
	{
		$this->notify();
	}
	
	/**
	 * Return the order reference number
	 * 
	 * @return int
	 */
	public function getRef()
	{
		return $this->iOrderRef;
	}
	
	/**
	 * Return the current order status
	 * 
	 * @return int
	 */
	public function getStatus()
	{
		return $this->iStatus;
	}
	
	/**
	 * Update the order status
	 */
	public function updateStatus($iStatus)
	{
		$this->notify();
		// ...
		$this->iStatus = $iStatus;
		// ...
		$this->notify();
	}
}

/**
 * Order status handler, observer that sends an email to secretary
 * if the status of an order changes from shipped to delivered, so the
 * secratary can make a phone call to our customer to ask for his opinion about the service
 * 
 * @package Shop
 */
class OrderStatusHandler implements SplObserver
{
	/**
	 * Previous orderstatus
	 * @var int
	 */
	protected $iPreviousOrderStatus;
	/**
	 * Current orderstatus
	 * @var int
	 */
	protected $iCurrentOrderStatus;
	
	/**
	 * Update, called by the observable object order
	 * 
	 * @param Observable_Interface $oSubject
	 * @param string $sEvent
	 * @param mixed $mData 
	 * @return void
	 */
	public function update(SplSubject $oSubject)
	{
		if(!$oSubject instanceof Order) {
			return;
		}
		if(is_null($this->iPreviousOrderStatus)) {
			$this->iPreviousOrderStatus = $oSubject->getStatus();
		} else {
			$this->iCurrentOrderStatus = $oSubject->getStatus();
			if($this->iPreviousOrderStatus === Order::STATUS_SHIPPED && $this->iCurrentOrderStatus === Order::STATUS_DELIVERED) {
				$sSubject = sprintf('Order number %d is shipped', $oSubject->getRef());
				//mail('secratary@example.com', 'Order number %d is shipped', 'Text');
				echo 'Mail sended to the secratary to help her remember to call our customer for a survey.';
			}
		}
	}
}

$oOrder = new Order(26012011);
$oOrder->attach(new OrderStatusHandler());
$oOrder->updateStatus(Order::STATUS_DELIVERED);
$oOrder->delete();
?>

There are several problems with the implementation above. To most important disadvantage is that we have only one update method in our observer. In this update method we don’t know when and why we are getting notified, just that something happened. We should keep track of everything that happens in the subject. (Or use debug_backtrace… just joking, don’t even think about using it that way ever!).

Taking it a step further, events
Lets take a look at the next example, we will extend the Observer implementation with some an additional parameter for the eventname that occured.

Finishing up, optional data

iOrderRef = $iOrderRef;
		
		// Get order information from the database or something else...
		$this->iStatus = Order::STATUS_SHIPPED;
	}
	
	/**
	 * Attach an observer
	 * 
	 * @param Observer_Interface $oObserver 
	 * @return void
	 */
	public function attachObserver(Observer_Interface $oObserver)
	{
		$sHash = spl_object_hash($oObserver);
		if (isset($this->aObservers[$sHash])) {
			throw new Exception('Observer is already attached');
		}

		$this->aObservers[$sHash] = $oObserver;
	}

	/**
	 * Detach observer
	 * 
	 * @param Observer_Interface $oObserver 
	 * @return void
	 */
	public function detachObserver(Observer_Interface $oObserver)
	{
		$sHash = spl_object_hash($oObserver);
		if (!isset($this->aObservers[$sHash])) {
			throw new Exception('Observer not attached');
		}
		unset($this->aObservers[$sHash]);
	}

	/**
	 * Notify the attached observers
	 * 
	 * @param string $sEvent, name of the event
	 * @param mixed $mData, optional data that is not directly available for the observers
	 * @return void
	 */
	public function notifyObserver($sEvent, $mData=null)
	{
		foreach ($this->aObservers as $oObserver) {
			try {
				$oObserver->update($this, $sEvent, $mData);
			} catch(Exception $e) {

			}
		}
	}

	/**
	 * Add an order
	 * 
	 * @param array $aOrder 
	 * @return void
	 */
	public function add($aOrder = array())
	{
		$this->notifyObserver('onAdd');
	}
	
	/**
	 * Return the order reference number
	 * 
	 * @return int
	 */
	public function getRef()
	{
		return $this->iOrderRef;
	}
	
	/**
	 * Return the current order status
	 * 
	 * @return int
	 */
	public function getStatus()
	{
		return $this->iStatus;
	}
	
	/**
	 * Update the order status
	 */
	public function updateStatus($iStatus)
	{
		$this->notifyObserver('onBeforeUpdateStatus');
		// ...
		$this->iStatus = $iStatus;
		// ...
		$this->notifyObserver('onAfterUpdateStatus');
	}
}

/**
 * Order status handler, observer that sends an email to secretary
 * if the status of an order changes from shipped to delivered, so the
 * secratary can make a phone call to our customer to ask for his opinion about the service
 * 
 * @package Shop
 */
class OrderStatusHandler implements Observer_Interface
{
	protected $iPreviousOrderStatus;
	protected $iCurrentOrderStatus;
	
	/**
	 * Update, called by the observable object order
	 * 
	 * @param Observable_Interface $oObservable
	 * @param string $sEvent
	 * @param mixed $mData 
	 * @return void
	 */
	public function update(Observable_Interface $oObservable, $sEvent, $mData=null)
	{
		if(!$oObservable instanceof Order) {
			return;
		}
		
		switch($sEvent) {
			case 'onBeforeUpdateStatus':
				$this->iPreviousOrderStatus = $oObservable->getStatus();
				return;
			case 'onAfterUpdateStatus':
				$this->iCurrentOrderStatus = $oObservable->getStatus();
				
				if($this->iPreviousOrderStatus === Order::STATUS_SHIPPED && $this->iCurrentOrderStatus === Order::STATUS_DELIVERED) {
					$sSubject = sprintf('Order number %d is shipped', $oObservable->getRef());
					//mail('secratary@example.com', 'Order number %d is shipped', 'Text');
					echo 'Mail sended to the secratary to help her remember to call our customer for a survey.';
				}
		}
	}
}

$oOrder = new Order(26012011);
$oOrder->attachObserver(new OrderStatusHandler());
$oOrder->updateStatus(Order::STATUS_DELIVERED);
$oOrder->add();
?>

Now we are able to take action on different events that occur.

Disadvantages
Although this implementation works quite well there are some drawbacks. One of those drawbacks is that we need to dispatch an event in our framework, if we don’t programmers can’t hook into our application. Triggering events everywhere give us a small performance penalty however I do think this way of working gives the programmers a nice way to hook into your application on those spots that you want them to hook in.

Just for the record
Notice that this code is just an example and can still use some improvements, for example: each observer is initialized even it will maybe never be notified, therefore I suggest to make use of lazy in some cases for loading the objects. There are other systems to hook into an application, more to follow!

Written by Sjoerd Maessen

May 23rd, 2011 at 8:02 pm

Posted in API

Tagged with modular, Observer, SPL, Subject

44,856 Responses to 'PHP hook, building hooks in your application'

Subscribe to comments with RSS or TrackBack to 'PHP hook, building hooks in your application'.

займы онлайн на карту 2025 займы онлайн без отказа

onlayn zaym 96

13 Sep 25 at 5:56 am
купить диплом колледжа [url=https://www.educ-ua10.ru]купить диплом колледжа[/url] .

Diplomi_xzKl

13 Sep 25 at 6:00 am
«Как отмечает врач-нарколог Алексей Николаевич Прудников, «выезд нарколога на дом — это возможность стабилизировать состояние пациента в привычной обстановке, снизив стресс и риски осложнений».»
Детальнее – [url=https://narkolog-na-dom-v-krasnodare14.ru/]вызвать нарколога на дом краснодар[/url]

PetermEn

13 Sep 25 at 6:01 am
электрический карниз для штор купить [url=https://www.karniz-s-elektroprivodom.ru]электрический карниз для штор купить[/url] .

karniz s elektroprivodom_hyKt

13 Sep 25 at 6:03 am
Приобрести диплом любого ВУЗа!
Наша компания предлагаетвыгодно и быстро заказать диплом, который выполняется на оригинальной бумаге и заверен мокрыми печатями, водяными знаками, подписями. Данный диплом пройдет лубую проверку, даже при помощи профессионального оборудования. Решите свои задачи быстро и просто с нашим сервисом- [url=http://dgr.juliusdigits.com/agent/mariedarker295/]dgr.juliusdigits.com/agent/mariedarker295[/url]

Jariorsck

13 Sep 25 at 6:03 am
Hey There. I found your blog using msn. This is a really well written article.
I will make sure to bookmark it and come back to
read more of your useful information. Thanks for the post.

I will definitely return.

Valentinstagsgrüße

13 Sep 25 at 6:04 am
электрокарнизы для штор [url=https://avtomaticheskie-karnizy-dlya-shtor.ru]электрокарнизы для штор[/url] .

avtomaticheskie karnizi dlya shtor_ijOr

13 Sep 25 at 6:04 am
займ денег онлайн займы онлайн на карту

zaym onlayn 540

13 Sep 25 at 6:05 am
электрокарнизы для штор [url=https://www.karnizy-s-elektroprivodom-cena.ru]электрокарнизы для штор[/url] .

karnizi s elektroprivodom cena_slkr

13 Sep 25 at 6:08 am
РџРµСЂРІС‹Р№ СЂР°Р· РІРёР¶Сѓ С‚Р°РєРѕРµ СЃ РњРќ. РћС‚ РґСЂСѓРіРёС… СЃРµР»Р»РµСЂРѕРІ РІСЃРµ Р±С‹Р»Рѕ РЅРѕСЂРј СЃ СЂР°СЃС‚РІРѕСЂРёРјРѕСЃС‚СЊСЋ. Р Р°СЃС‚РІРѕСЂСЏСЋС‰РёР№СЃСЏ РїРѕР»РЅРѕСЃС‚СЊСЋ РїРµСЂ С‡СѓС‚СЊ РїРѕСЃРёР»СЊРЅРµРµ…
https://www.impactio.com/researcher/yodamanilikelife64
РІСЃРµРј Р¶РµР»Р°СЋ СЃС‡Р°СЃС‚СЊСЏ!

Harryunsag

13 Sep 25 at 6:09 am
электрокарнизы [url=http://www.avtomaticheskie-karnizy-dlya-shtor.ru]электрокарнизы[/url] .

avtomaticheskie karnizi dlya shtor_qnOr

13 Sep 25 at 6:10 am
карниз электро [url=https://karniz-s-elektroprivodom.ru]карниз электро[/url] .

karniz s elektroprivodom_zgKt

13 Sep 25 at 6:10 am
купить диплом младшего специалиста в украине [url=https://educ-ua10.ru]купить диплом младшего специалиста в украине[/url] .

Diplomi_pqKl

13 Sep 25 at 6:10 am
This article will assist the internet viewers for setting up new webpage or even a blog from start to end.

slot gacor

13 Sep 25 at 6:12 am
электрокарниз [url=http://karnizy-s-elektroprivodom-cena.ru/]электрокарниз[/url] .

karnizi s elektroprivodom cena_elkr

13 Sep 25 at 6:13 am
электрокарнизы купить в москве [url=www.avtomaticheskie-karnizy-dlya-shtor.ru/]электрокарнизы купить в москве[/url] .

avtomaticheskie karnizi dlya shtor_cbOr

13 Sep 25 at 6:14 am
It’s a shame you don’t have a donate button! I’d most certainly donate to this excellent blog!

I guess for now i’ll settle for book-marking and adding your RSS feed
to my Google account. I look forward to new updates and will talk about this
site with my Facebook group. Talk soon!

casino

13 Sep 25 at 6:15 am
карниз для штор электрический [url=https://elektro-karniz77.ru]https://elektro-karniz77.ru[/url] .

elektro karniz_swSl

13 Sep 25 at 6:15 am
автоматические гардины для штор [url=https://avtomaticheskie-karnizy.ru]https://avtomaticheskie-karnizy.ru[/url] .

avtomaticheskie karnizi_xnSa

13 Sep 25 at 6:15 am
электрокарнизы для штор купить [url=https://karnizy-s-elektroprivodom-cena.ru]электрокарнизы для штор купить[/url] .

karnizi s elektroprivodom cena_vfkr

13 Sep 25 at 6:15 am
электрические гардины [url=https://elektrokarniz-cena.ru]электрические гардины[/url] .

elektrokarniz cena_syPL

13 Sep 25 at 6:17 am
1win 500% [url=www.1win12004.ru]www.1win12004.ru[/url]

1win_fqEr

13 Sep 25 at 6:17 am
Этот комплекс мер позволяет оказывать помощь пациентам на всех стадиях зависимости.
Получить больше информации – http://narkologicheskaya-klinika-sankt-peterburg14.ru

Romanronse

13 Sep 25 at 6:19 am
гардина с электроприводом [url=http://karniz-s-elektroprivodom.ru]гардина с электроприводом[/url] .

karniz s elektroprivodom_haKt

13 Sep 25 at 6:21 am
Usually I do not learn article on blogs, but I
wish to say that this write-up very pressured me to check out and do it!
Your writing taste has been surprised me. Thanks, quite
great post.

หวยลาววันนี้

13 Sep 25 at 6:22 am
Hurrah, that’s what I was searching for, what a material!
present here at this web site, thanks admin of this web site.

CruvionaPro

13 Sep 25 at 6:24 am
«Как отмечает врач-нарколог Алексей Николаевич Прудников, «выезд нарколога на дом — это возможность стабилизировать состояние пациента в привычной обстановке, снизив стресс и риски осложнений».»
Подробнее тут – [url=https://narkolog-na-dom-v-krasnodare14.ru/]платный нарколог на дом в краснодаре[/url]

Robertosaids

13 Sep 25 at 6:24 am
покупка курсовых курсовая работа на заказ

kursovaya-rabota-539

13 Sep 25 at 6:24 am
автоматический карниз для штор [url=https://www.karniz-s-elektroprivodom.ru]автоматический карниз для штор[/url] .

karniz s elektroprivodom_kqKt

13 Sep 25 at 6:24 am
Заказать диплом университета!
Мы предлагаемвыгодно и быстро приобрести диплом, который выполнен на оригинальном бланке и заверен печатями, водяными знаками, подписями. Документ пройдет лубую проверку, даже с применением специфических приборов. Решите свои задачи быстро и просто с нашей компанией- [url=http://pikenepatorvet.no/2025/08/gde-kupit-diplom-v-2025-godu-bez-riska-70/]pikenepatorvet.no/2025/08/gde-kupit-diplom-v-2025-godu-bez-riska-70[/url]

Jariorypg

13 Sep 25 at 6:28 am
карнизы для штор купить в москве [url=https://avtomaticheskie-karnizy-dlya-shtor.ru/]карнизы для штор купить в москве[/url] .

avtomaticheskie karnizi dlya shtor_kwOr

13 Sep 25 at 6:31 am
электрокарниз недорого [url=https://www.elektrokarniz-cena.ru]https://www.elektrokarniz-cena.ru[/url] .

elektrokarniz cena_qqPL

13 Sep 25 at 6:32 am
микрозаймы онлайн первый Понравилась скорость обработки заявки на микрозайм онлайн 30 дней. Все очень удобно!

Brentjig

13 Sep 25 at 6:32 am
Actually no matter if someone doesn’t know afterward its up to other people that they will help,
so here it occurs.

jual narkoba murah

13 Sep 25 at 6:32 am
скачать казино мостбет [url=https://mostbet12008.ru/]https://mostbet12008.ru/[/url]

mostbet_uuer

13 Sep 25 at 6:33 am
РђРґРµРєРІР°С‚РЅС‹Рј Р»СЋРґСЏРј С†РµРЅСЏС‰РёС… РїСЂРѕС„С„РµСЃРёР°РЅРѕР»РёР·Рј СЂРµРєРѕРјРµРЅРґСѓСЋ СЂРµР°РєС‚РёРІС‹ С‚СѓС‚ С‚Р°СЂРёС‚СЊ…
https://yamap.com/users/4806634
СЃРјРѕС‚СЂСЏ РєР°РєРёРј СЂРµР°РіРµРЅС‚РѕРј Р±СѓРґРµС€СЊ Р±Р°РґСЏР¶РёС‚СЊ

Harryunsag

13 Sep 25 at 6:33 am
скачать мостбет на андроид [url=https://mostbet12008.ru]https://mostbet12008.ru[/url]

mostbet_vxer

13 Sep 25 at 6:33 am
карниз электро [url=avtomaticheskie-karnizy-dlya-shtor.ru]карниз электро[/url] .

avtomaticheskie karnizi dlya shtor_hxOr

13 Sep 25 at 6:34 am
мосвет казино [url=www.mostbet12008.ru]мосвет казино[/url]

mostbet_iler

13 Sep 25 at 6:35 am
Заказать диплом ВУЗа!
Мы предлагаемвыгодно купить диплом, который выполняется на оригинальном бланке и заверен мокрыми печатями, водяными знаками, подписями официальных лиц. Наш документ пройдет лубую проверку, даже с применением специфических приборов. Решайте свои задачи максимально быстро с нашими дипломами- [url=http://pad.stuve.uni-ulm.de/s/L3gVayJZt/]pad.stuve.uni-ulm.de/s/L3gVayJZt[/url]

Jariornpn

13 Sep 25 at 6:35 am
https://impossible-studio.ghost.io/kak-vybrat-luchshii-vpn-siervis-podrobnoie-rukovodstvo/ Новый лонгрид про Youtuber VPN! Узнайте, как смотреть YouTube и другие платформы без лагов и блокировок. Подключайте до 5 устройств на одной подписке, тестируйте сервис бесплатно 3 дня и платите всего 290? в первый месяц вместо 2000? у конкурентов. Серверы в Европе — ваши данные защищены от российских властей.

Kevintow

13 Sep 25 at 6:35 am
карнизы для штор купить в москве [url=https://elektrokarniz-cena.ru]карнизы для штор купить в москве[/url] .

elektrokarniz cena_ptPL

13 Sep 25 at 6:35 am
автоматические карнизы для штор [url=https://www.avtomaticheskie-karnizy-dlya-shtor.ru]автоматические карнизы для штор[/url] .

avtomaticheskie karnizi dlya shtor_htOr

13 Sep 25 at 6:36 am
моствет [url=http://mostbet12009.ru/]http://mostbet12009.ru/[/url]

mostbet_mgsl

13 Sep 25 at 6:36 am
Please let me know if you’re looking for a article writer for your weblog.
You have some really great articles and I think I would be a good asset.
If you ever want to take some of the load off, I’d absolutely love
to write some material for your blog in exchange for a link back to mine.
Please send me an email if interested. Thank you!

Velar Paynex

13 Sep 25 at 6:37 am
Анонимность — важнейшее условие обращения за помощью. В клинике действуют не декларации, а конкретные технологические и организационные меры, которые защищают пациента и его близких от стигмы и лишнего обсуждения.
Получить дополнительную информацию – http://narkologicheskaya-klinika-rostov-na-donu14.ru/narkolog-rostov-na-donu/

Jackiemoips

13 Sep 25 at 6:41 am
автоматические карнизы [url=http://www.elektro-karniz77.ru]http://www.elektro-karniz77.ru[/url] .

elektro karniz_xgSl

13 Sep 25 at 6:41 am
карниз с приводом для штор [url=http://avtomaticheskie-karnizy.ru/]http://avtomaticheskie-karnizy.ru/[/url] .

avtomaticheskie karnizi_rkSa

13 Sep 25 at 6:41 am
Excellent post. I was checking constantly this weblog
and I am inspired! Very useful information particularly the
remaining phase 🙂 I take care of such info much. I was looking for this certain info for a very lengthy time.
Thank you and good luck.

audit firm singapore

13 Sep 25 at 6:42 am
карниз с приводом [url=http://www.elektrokarniz-cena.ru]http://www.elektrokarniz-cena.ru[/url] .

elektrokarniz cena_mlPL

13 Sep 25 at 6:44 am

Winkans bij loterijen

Pokersites voor Enschedeers

Sjoerd Maessen blog

PHP hook, building hooks in your application

44,856 Responses to 'PHP hook, building hooks in your application'

Leave a Reply

Archive

Recent Comments

Tags

Meta