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!
ставки прогнозы [url=www.stavka-10.ru]www.stavka-10.ru[/url] .
stavka_ysSi
16 Oct 25 at 11:35 pm
Kaizenaire.com succeeds іn aggregating Singapore’ѕ promotions frߋm preferred firms ɑnd brand names.
Cօnstantly chasing worth, Singaporeans discover bliss іn Singapore’s promotion-filled shopping paradise.
Diving trips tо neighboring islands adventure undersea travelers fｒom Singapore, and keｅp
іn mind to stay upgraded ᧐n Singapore’s most current promotions and shopping deals.
Depayser layouts mіnimal garments witһ а French style, cherished bʏ elegant Singaporeans fоr theiｒ simple and easy beauty.
SPC supplies oil items аnd benefit store products ѕia, adored ƅy Singaporeans fоr
tһeir gas effectiveness programs ɑnd on-the-go snacks lah.
Killiney Kopijtiam brews standard kopi аnd salute, treasured f᧐r traditional appeal ɑnd
strong regional coffee.
Мuch ƅetter rush lor, check out Kaizenaire.com daily f᧐r shopping mah.
Feel free tⲟ surf to mʏ webpage: hairy crab promotions
hairy crab promotions
16 Oct 25 at 11:38 pm
Kaizenaire.c᧐m excels as the ultimate curator օf Singapore’s shopping
promotions.
Singaporeans ɑlways commemorate deals іn tһeir city’ѕ renowned
shopping paradise.
Тaking part in dragon watercraft races builds synergy аmong adventurous
Singaporeans, ɑnd kеep in mind to stay upgraded on Singapore’s
latest promotions ɑnd shopping deals.
Graye focuses ᧐n contemporary menswear, valued
Ƅү dapper Singaporeans f᧐r their tailored fits and modern lookѕ.
Masion, liкely а style label lah, supplies elegant clothing lor, valued
ƅy graceful Singaporeans fօr thеіr refined styles leh.
Nation Foods refines fowl аnd meats, precious fоr fresh materials іn neighborhood
markets.
Wah, so amazing ѕia, Kaizenaire.ϲom consistently features brand-new discount rates
lor.
Αlso visit my pagе … Kaizenaire Philippines Offshoring
Kaizenaire Philippines Offshoring
16 Oct 25 at 11:38 pm
I’m really loving the theme/design of your web site.
Do you ever run into any web browser compatibility issues?
A few of my blog audience have complained about my site not operating correctly in Explorer but
looks great in Opera. Do you have any tips to help fix this
issue?
Finxor GPT Avis
16 Oct 25 at 11:42 pm
Its such as you learn my thoughts! You seem to know a lot approximately this, like you wrote the ebook in it or something.
I think that you can do with a few p.c. to force the message home a bit, but instead of
that, that is fantastic blog. A great read. I will definitely be back.
aborsi gratis
16 Oct 25 at 11:45 pm
спортивные трансляции [url=http://www.novosti-sporta-16.ru]http://www.novosti-sporta-16.ru[/url] .
novosti sporta_lssi
16 Oct 25 at 11:45 pm
прогнозы на спорт на завтра [url=www.prognozy-na-sport-11.ru/]прогнозы на спорт на завтра[/url] .
prognozi na sport_slPa
16 Oct 25 at 11:47 pm
linebet ????
????? ??? linebet
16 Oct 25 at 11:49 pm
mostbet uz [url=https://mostbet4185.ru]https://mostbet4185.ru[/url]
mostbet_uz_smer
16 Oct 25 at 11:50 pm
Этап вывода из запоя
Подробнее тут – https://vyvod-iz-zapoya-shchelkovo6.ru/pomoshch-vyvod-iz-zapoya-v-shchelkovo/
VictorVok
16 Oct 25 at 11:53 pm
Деревянные лестницы https://rosslestnica.ru под заказ в любом стиле. Прямые, винтовые, маршевые конструкции из массива. Замеры, 3D-проект, доставка и установка. Гарантия качества и точности исполнения.
rosslestnica-2
16 Oct 25 at 11:54 pm
https://t.me/Official_1xbet_1xbet/s/1304
AlbertEnark
16 Oct 25 at 11:55 pm
Откройте для себя прекрасные и загадочные места, которые находятся под охраной в нашей стране.
Хочу выделить материал про Изучение ООПТ России: парки, заповедники, водоемы.
Вот, можете почитать:
[url=https://alloopt.ru]https://alloopt.ru[/url]
Надеюсь, вы нашли это путешествие по природе познавательным.
fixRow
16 Oct 25 at 11:56 pm
Деревянные лестницы https://rosslestnica.ru под заказ в любом стиле. Прямые, винтовые, маршевые конструкции из массива. Замеры, 3D-проект, доставка и установка. Гарантия качества и точности исполнения.
rosslestnica-451
16 Oct 25 at 11:57 pm
The Minotaurus presale vesting program is a game-changer for early birds. Extend for bonuses and avoid FOMO on post-TGE pumps. $MTAUR could be the dark horse in blockchain games.
minotaurus token
WilliamPargy
16 Oct 25 at 11:57 pm
прогнозы на сегодня спорт [url=https://prognozy-na-sport-12.ru/]прогнозы на сегодня спорт[/url] .
prognozi na sport_ctMn
16 Oct 25 at 11:57 pm
This website truly has all the information and facts
I wanted about this subject and didn’t know who to ask.
Pink salt recipe
16 Oct 25 at 11:58 pm
Лестницы в Москве https://лестницы-в-москве.рф продажа и изготовление под заказ. Прямые, винтовые, модульные и чердачные конструкции. Качество, гарантия и монтаж по всем стандартам.
lestnicy-v-moskve-785
16 Oct 25 at 11:59 pm
При тяжелых формах алкогольной интоксикации своевременное вмешательство критически важно для предотвращения опасных осложнений. В Луганске ЛНР специалисты по наркологии предоставляют услугу экстренной капельничной терапии на дому, что позволяет быстро снизить токсическую нагрузку и стабилизировать работу жизненно важных органов. Такой метод лечения позволяет обеспечить высокую эффективность терапии в комфортной, привычной для пациента обстановке, при этом сохраняется полная конфиденциальность.
Выяснить больше – [url=https://kapelnica-ot-zapoya-lugansk-lnr00.ru/]капельница от запоя вызов[/url]
JarredToulp
16 Oct 25 at 11:59 pm
https://t.me/Official_1xbet_1xbet/s/1477
AlbertEnark
17 Oct 25 at 12:00 am
купить диплом в новомосковске [url=www.rudik-diplom2.ru]купить диплом в новомосковске[/url] .
Diplomi_rupi
17 Oct 25 at 12:00 am
https://t.me/Official_1xbet_1xbet/s/719
AlbertEnark
17 Oct 25 at 12:00 am
Для загрузки десктопного клиента Pokerdom обратитесь в службу технической поддержки — специалисты предоставят актуальную ссылку для установки.
покердом казино
17 Oct 25 at 12:00 am
mostvet [url=mostbet4182.ru]mostbet4182.ru[/url]
mostbet_uz_sakt
17 Oct 25 at 12:01 am
The $MTAUR token utility in unlocking special zones is what sets it apart from generic play-to-earn. Presale stage 1 savings are massive, up to 5x value. Team’s experience from top crypto projects adds credibility.
minotaurus ico
WilliamPargy
17 Oct 25 at 12:01 am
В «АльтерМед» используются самые актуальные технологии, прошедшие проверку временем и доказавшие эффективность в тысячах клинических случаев. Выбор методики зависит от тяжести зависимости, состояния здоровья, наличия хронических заболеваний, прошлых попыток лечения и психологической мотивации пациента.
Подробнее – https://kodirovanie-ot-alkogolizma-dolgoprudnyj6.ru/
Robertlem
17 Oct 25 at 12:01 am
прогнозы на спорт на сегодня от профессионалов [url=http://prognozy-na-sport-12.ru]прогнозы на спорт на сегодня от профессионалов[/url] .
prognozi na sport_upMn
17 Oct 25 at 12:01 am
I love it when individuals come together and share thoughts.
Great website, stick with it!
Trade Vector AI
17 Oct 25 at 12:02 am
аналитика ставок [url=https://www.stavka-12.ru]https://www.stavka-12.ru[/url] .
stavka_ziSi
17 Oct 25 at 12:02 am
прогнозы и ставки на спорт [url=https://prognozy-na-sport-11.ru/]prognozy-na-sport-11.ru[/url] .
prognozi na sport_gpPa
17 Oct 25 at 12:02 am
Лестницы в Москве https://лестницы-в-москве.рф продажа и изготовление под заказ. Прямые, винтовые, модульные и чердачные конструкции. Качество, гарантия и монтаж по всем стандартам.
lestnicy-v-moskve-133
17 Oct 25 at 12:03 am
купить телефон спб [url=http://kupit-telefon-samsung-2.ru/]купить телефон спб[/url] .
kypit telefon samsyng_sqen
17 Oct 25 at 12:04 am
купить проведенный диплом высокие [url=https://frei-diplom1.ru]купить проведенный диплом высокие[/url] .
Diplomi_mxOi
17 Oct 25 at 12:04 am
I used to be able to find good information from your content.
do australians need visa for turkey
17 Oct 25 at 12:07 am
где купить диплом колледжа в омске [url=https://frei-diplom7.ru/]https://frei-diplom7.ru/[/url] .
Diplomi_kuei
17 Oct 25 at 12:11 am
Asking questions are genuinely pleasant thing if you are not understanding anything entirely,
except this article presents good understanding even.
visa for turkey from australia
17 Oct 25 at 12:11 am
купить официальный диплом с занесением в реестр [url=frei-diplom2.ru]frei-diplom2.ru[/url] .
Diplomi_fjEa
17 Oct 25 at 12:11 am
спорт онлайн [url=https://novosti-sporta-16.ru/]https://novosti-sporta-16.ru/[/url] .
novosti sporta_imsi
17 Oct 25 at 12:12 am
купить диплом в дзержинске техникум [url=www.frei-diplom9.ru/]купить диплом в дзержинске техникум[/url] .
Diplomi_pcea
17 Oct 25 at 12:16 am
новости легкой атлетики [url=https://novosti-sporta-16.ru/]https://novosti-sporta-16.ru/[/url] .
novosti sporta_fssi
17 Oct 25 at 12:17 am
At this time it seems like Movable Type is the preferred blogging platform out
there right now. (from what I’ve read) Is that what you are using on your blog?
mag 60 paste
17 Oct 25 at 12:19 am
https://t.me/Official_1xbet_1xbet/s/918
AlbertEnark
17 Oct 25 at 12:20 am
https://t.me/Official_1xbet_1xbet/s/1222
AlbertEnark
17 Oct 25 at 12:21 am
прогнозы на ставки бесплатно [url=https://prognozy-na-sport-11.ru/]prognozy-na-sport-11.ru[/url] .
prognozi na sport_ikPa
17 Oct 25 at 12:22 am
прогноз букмекеров [url=https://stavka-12.ru]прогноз букмекеров[/url] .
stavka_ioSi
17 Oct 25 at 12:23 am
телефон самсунг купить спб [url=https://kupit-telefon-samsung-2.ru/]https://kupit-telefon-samsung-2.ru/[/url] .
kypit telefon samsyng_xaen
17 Oct 25 at 12:24 am
Дополнительным нововведением стало добавление раздела
со спортивными ставками.
вавада официальный сайт вход зеркало
17 Oct 25 at 12:25 am
диплом с занесением в реестр купить [url=http://www.frei-diplom3.ru]диплом с занесением в реестр купить[/url] .
Diplomi_azKt
17 Oct 25 at 12:25 am
https://t.me/Official_1xbet_1xbet/s/335
AlbertEnark
17 Oct 25 at 12:25 am
Каждая инновация начинается с кода kraken официальные ссылки kraken онион kraken онион тор кракен онион
RichardPep
17 Oct 25 at 12:26 am