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!
заказать продвижение сайта в москве [url=https://internet-agentstvo-prodvizhenie-sajtov-seo.ru/]заказать продвижение сайта в москве[/url] .
internet agentstvo prodvijenie saitov seo_brot
5 Sep 25 at 12:03 am
https://english.stackexchange.com/users/787016/1xbet-casino-promo-code?tab=profile
Raymondvop
5 Sep 25 at 12:04 am
Когда следует немедленно обращаться за помощью:
Изучить вопрос глубже – http://алко-ребцентр.рф
Gerardohob
5 Sep 25 at 12:04 am
поисковое seo в москве [url=https://poiskovoe-seo-v-moskve.ru/]poiskovoe-seo-v-moskve.ru[/url] .
poiskovoe seo v moskve_vhPr
5 Sep 25 at 12:05 am
https://www.ptwmonksupply.com/forum/topic/8126/mmoexp–through-this-guide,-you-should-have-a-clear-understanding&p=52
Raymondvop
5 Sep 25 at 12:05 am
Thanks for the auspicious writeup. It if truth
be told used to be a leisure account it. Glance advanced to far introduced
agreeable from you! By the way, how could we keep in touch?
website
5 Sep 25 at 12:06 am
продвижения сайта в google [url=internet-agentstvo-prodvizhenie-sajtov-seo.ru]продвижения сайта в google[/url] .
internet agentstvo prodvijenie saitov seo_quot
5 Sep 25 at 12:07 am
Create Rss Feed For Your Website And Display Rss Feed website, Jami,
Jami
5 Sep 25 at 12:08 am
seo partners [url=https://poiskovoe-seo-v-moskve.ru/]https://poiskovoe-seo-v-moskve.ru/[/url] .
poiskovoe seo v moskve_exPr
5 Sep 25 at 12:10 am
평소에는 참아내기 바빴던 감정들이 여성전용마사지의 따뜻한 손길 앞에서는 조심스레 스며
나와, 다시 나답게 살아갈 용기를 얻을
수 있었어요.
서울여성전용마사지
5 Sep 25 at 12:10 am
букмекерская. контора. мостбет. [url=http://mostbet4130.ru/]http://mostbet4130.ru/[/url]
mostbet_kg_ccpr
5 Sep 25 at 12:11 am
https://pharmaexpressfrance.shop/# trouver un mГ©dicament en pharmacie
WilliamTeeli
5 Sep 25 at 12:11 am
мостбет на футбол ставки [url=http://mostbet4167.ru/]http://mostbet4167.ru/[/url]
mostbet_xzKa
5 Sep 25 at 12:11 am
Мы предлагаем документы университетов, которые находятся на территории всей России. Приобрести диплом о высшем образовании:
[url=http://wp.nootheme.com/jobmonster/dummy2/companies/ukrdiplom/]купить аттестат за 11 классов оригинал[/url]
Diplomi_xuPn
5 Sep 25 at 12:11 am
Вывод из запоя — это комплексная медицинская процедура, направленная на очищение организма, стабилизацию психоэмоционального состояния и восстановление нормального самочувствия. В клинике «Операция Здоровье» пациенты могут получить помощь в стационаре или с выездом врача на дом. Мы работаем круглосуточно, обеспечивая безопасность и анонимность лечения.
Подробнее можно узнать тут – https://наркология-дома.рф/vyvod-iz-zapoya-czena-v-krasnodare/
RaymondTup
5 Sep 25 at 12:12 am
Банва Частный Остров
Brandongal
5 Sep 25 at 12:17 am
Ищете источник ежедневной мотивации заботиться о себе? «Здоровье и гармония» — это понятные советы по красоте, здоровью и психологии, которые делают жизнь легче и радостнее. Даем разборы привычек, практичные лайфхаки и истории для вдохновения — никакой воды и сложностей. Посмотрите свежие статьи и сохраните понравившиеся для практики уже сегодня: https://xn--80aafh2aajttqcc0jrc.xn--p1ai/ Делайте маленькие шаги — результат удивит, а поддержка экспертных материалов поможет не свернуть с пути.
NisipScusa
5 Sep 25 at 12:17 am
купить диплом об образовании с реестром [url=https://educ-ua13.ru]купить диплом об образовании с реестром[/url] .
Diplomi_fapn
5 Sep 25 at 12:19 am
продвижение сайтов в москве [url=http://internet-agentstvo-prodvizhenie-sajtov-seo.ru]продвижение сайтов в москве[/url] .
internet agentstvo prodvijenie saitov seo_biot
5 Sep 25 at 12:23 am
поисковое продвижение сайта в интернете москва [url=poiskovoe-seo-v-moskve.ru]poiskovoe-seo-v-moskve.ru[/url] .
poiskovoe seo v moskve_ynPr
5 Sep 25 at 12:26 am
После первичной диагностики начинается активная фаза лечения. Современные медикаменты вводятся капельничным методом для быстрого выведения токсинов из организма и восстановления нормальных обменных процессов. Этот этап критически важен для нормализации работы печени, почек и сердечно-сосудистой системы.
Ознакомиться с деталями – [url=https://reabcentr-narko.ru/]наркологический вывод из запоя[/url]
KennethHet
5 Sep 25 at 12:26 am
мостбет скачать приложение [url=https://www.mostbet4165.ru]https://www.mostbet4165.ru[/url]
mostbet_qfMn
5 Sep 25 at 12:29 am
комплектная трансформаторная подстанция купить [url=http://dimitrov.forum24.ru/?1-8-0-00000222-000-0-0]комплектная трансформаторная подстанция купить[/url] .
transformatornie podstancii _pver
5 Sep 25 at 12:30 am
узи аппарат купить цена [url=www.kupit-uzi-apparat27.ru]узи аппарат купить цена[/url] .
kypit yzi apparat_nrSl
5 Sep 25 at 12:32 am
Мы предлагаем документы ВУЗов, которые расположены в любом регионе России. Купить диплом о высшем образовании:
[url=http://bnsgh.com/read-blog/21233_attestat-o-polnom-srednem-obrazovanii-kupit.html/]купить аттестат за 11 класс спб отзывы[/url]
Diplomi_gyPn
5 Sep 25 at 12:33 am
고된 일상 속, 토닥이에서의
시간은 저만의 작은 휴가처럼 느껴졌습니다.
토닥이
5 Sep 25 at 12:35 am
No matter whether your roofing project is big or small, you can count on our commitment and use of the finest roofing materials to handle the job correctly.
storage.googleapis.com
5 Sep 25 at 12:35 am
303Hoki adalah layanan pengiriman terpercaya yang menawarkan kecepatan, keamanan, dan harga terjangkau.
Dengan 303Hoki, pelanggan dapat mengirim barang
ke seluruh Indonesia dengan kualitas pelayanan terbaik.
303hoki
5 Sep 25 at 12:37 am
В Люберцах капельница от запоя может спасти здоровье — в Stop Alko работают опытные наркологи, которые точно знают, как снять интоксикацию без вреда.
Подробнее тут – [url=https://kapelnica-ot-zapoya-lyubercy13.ru/]капельница от запоя цена подольск[/url]
MichaelAreld
5 Sep 25 at 12:39 am
Dive гight into Kaizenaire.com, Singapore’s premier aggregator
ߋf shopping promotions аnd unique brand namｅ deals.
Singaporeans embrace tһeir internal deal hunters іn Singapore, the shopping heaven overflowing ᴡith promotions and
unique deals.
Attending health resorts rejuvenates tired Singaporeans, аnd keeρ in mind to remaіn upgraded
on Singapore’s latеst promotions and shopping deals.
Ԍreat Eastern սses life insurance policy and health care plans, beloved
Ƅy Singaporeans fߋr their detailed protection ɑnd comfort in unsure timeѕ.
Sabrin Goh develops lasting fashion pieces leh, preferred Ƅy
ecologically mindful Singaporeans fߋr theіr eco-chic
layouts օne.
SIS Sugar sweetens ᴡith improved sugars, enjoyed
fⲟr cooking basics in Singaporean households.
Auntie ѕuggest leh, check Kaizenaire.com daily fߋr cost savings one.
Here is my web blog Promotions Singapore
Promotions Singapore
5 Sep 25 at 12:39 am
Мы можем предложить документы любых учебных заведений, которые расположены в любом регионе России. Приобрести диплом любого ВУЗа:
[url=http://job4thai.com/profile/marcelo900295/]купить аттестат 11 классов челябинск[/url]
Diplomi_mkPn
5 Sep 25 at 12:40 am
продвижение сайтов интернет магазины в москве [url=http://www.internet-agentstvo-prodvizhenie-sajtov-seo.ru]продвижение сайтов интернет магазины в москве[/url] .
internet agentstvo prodvijenie saitov seo_hgot
5 Sep 25 at 12:40 am
распродажа дизайнерской мебели [url=www.dizajnerskaya-mebel-1.ru/]распродажа дизайнерской мебели[/url] .
dizainerskaya mebel_sxEr
5 Sep 25 at 12:41 am
защитная пленка для поверхностей [url=http://samokleyushchayasya-plenka-1.ru/]http://samokleyushchayasya-plenka-1.ru/[/url] .
plenka samokleushayasya zashitnaya_dnma
5 Sep 25 at 12:42 am
продвижения сайта в google [url=www.poiskovoe-seo-v-moskve.ru/]www.poiskovoe-seo-v-moskve.ru/[/url] .
poiskovoe seo v moskve_ddPr
5 Sep 25 at 12:43 am
Ламу
Brandongal
5 Sep 25 at 12:45 am
трансформаторные подстанции купить [url=http://www.www.bisound.com/forum/showthread.php?t=1984168]трансформаторные подстанции купить[/url] .
transformatornie podstancii _uder
5 Sep 25 at 12:45 am
аудит продвижения сайта [url=https://internet-agentstvo-prodvizhenie-sajtov-seo.ru/]аудит продвижения сайта[/url] .
internet agentstvo prodvijenie saitov seo_ukot
5 Sep 25 at 12:45 am
mostbet uz ilova bilan ro‘yxatdan o‘tish [url=mostbet4169.ru]mostbet uz ilova bilan ro‘yxatdan o‘tish[/url]
mostbet_jlSt
5 Sep 25 at 12:46 am
I enjoy, cause I discovered exactly what I
was looking for. You’ve ended my 4 day long hunt!
God Bless you man. Have a nice day. Bye
luxury black car service
5 Sep 25 at 12:46 am
seo network [url=http://poiskovoe-seo-v-moskve.ru]http://poiskovoe-seo-v-moskve.ru[/url] .
poiskovoe seo v moskve_dpPr
5 Sep 25 at 12:48 am
мостбет скачать на андроид [url=http://mostbet4128.ru]http://mostbet4128.ru[/url]
mostbet_kg_weot
5 Sep 25 at 12:52 am
seo network [url=https://www.internet-agentstvo-prodvizhenie-sajtov-seo.ru]seo network[/url] .
internet agentstvo prodvijenie saitov seo_bsot
5 Sep 25 at 12:53 am
раскрутка и продвижение сайта [url=https://poiskovoe-seo-v-moskve.ru]раскрутка и продвижение сайта[/url] .
poiskovoe seo v moskve_qmPr
5 Sep 25 at 12:56 am
аппарат узи цена [url=https://kupit-uzi-apparat27.ru/]аппарат узи цена[/url] .
kypit yzi apparat_wmSl
5 Sep 25 at 12:57 am
Boost Your Search Enginje Ranking By Weeb Copywriting Outside Your Webwite website (Melba)
Melba
5 Sep 25 at 1:02 am
поисковое seo в москве [url=www.internet-agentstvo-prodvizhenie-sajtov-seo.ru]www.internet-agentstvo-prodvizhenie-sajtov-seo.ru[/url] .
internet agentstvo prodvijenie saitov seo_yeot
5 Sep 25 at 1:07 am
купить диплом о высшем образовании легально [url=https://educ-ua13.ru]https://educ-ua13.ru[/url] .
Diplomi_gxpn
5 Sep 25 at 1:09 am
Howdy! This post couldn’t be written much better!
Looking at this post reminds me of my previous roommate!
He constantly kept preaching about this. I’ll forward this
information to him. Pretty sure he’s going to have a good read.
Many thanks for sharing!
портал игра
5 Sep 25 at 1:11 am
поисковое продвижение москва профессиональное продвижение сайтов [url=http://poiskovoe-seo-v-moskve.ru]http://poiskovoe-seo-v-moskve.ru[/url] .
poiskovoe seo v moskve_knPr
5 Sep 25 at 1:11 am