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!
Great post. I was checking constantly this blog and I am impressed!
Very useful information particularly the last part 🙂 I care for
such info much. I was seeking this particular information for a very long time.
Thank you and good luck.
X88
3 Oct 25 at 7:41 am
купить диплом занесением реестр киев [url=https://frei-diplom4.ru/]https://frei-diplom4.ru/[/url] .
Diplomi_hgOl
3 Oct 25 at 7:41 am
При превышении лимита оператор будет списывать 5-10% от суммы транзакции.
казино 7к
3 Oct 25 at 7:42 am
I’m pretty pleased to discover this website. I wanted to thank you
for ones time just for this wonderful read!! I definitely appreciated every part of it and i also have you bookmarked to see new stuff in your website.
Immutable Azopt
3 Oct 25 at 7:42 am
прогноз матчей ставки на спорт [url=http://www.stavka-12.ru]http://www.stavka-12.ru[/url] .
stavka_bhSi
3 Oct 25 at 7:43 am
Appreciate this post. Let me try it out.
Buy Tapentadol Without Prescription
3 Oct 25 at 7:43 am
новости легкой атлетики [url=http://novosti-sporta-16.ru/]http://novosti-sporta-16.ru/[/url] .
novosti sporta_egsi
3 Oct 25 at 7:46 am
Big thanks for the glory casino platform — super useful!
https://glory-casino-bangladesh.pw/bonus
https://glory-casino-bangladesh.pw/registration
3 Oct 25 at 7:46 am
The other day, while I was at work, my sister stole my iPad
and tested to see if it can survive a twenty five foot drop, just so she can be a youtube sensation. My
iPad is now destroyed and she has 83 views.
I know this is completely off topic but I had to share it with someone!
Lunel Bitrow Erfahrungen
3 Oct 25 at 7:47 am
Этот информативный материал предлагает содержательную информацию по множеству задач и вопросов. Мы призываем вас исследовать различные идеи и факты, обобщая их для более глубокого понимания. Наша цель — сделать обучение доступным и увлекательным.
Прочитать подробнее – https://www.crufaoci.org/rentree-solennelle-des-universites-publiques-de-cote-divoire
MyrtleLox
3 Oct 25 at 7:48 am
OMT’s updated resources maintain math fresh аnd amazing, motivating Singapore students tⲟ
embrace іt totally f᧐r examination victories.
Օpen your child’ѕ cоmplete potential іn mathematics ᴡith OMT Math Tuition’s expert-led classes, tailored tο Singapore’ѕ
MOE syllabus fօr primary, secondary, аnd JC students.
Αs mathematics underpins Singapore’ѕ credibility fߋr quality іn global benchmarks ⅼike PISA, math tuition іs crucial to unlocking a
kid’s potential and securing academic advantages іn this cokre subject.
primary school math tuition builds examination stamina tһrough timed drills, imitating tһｅ PSLE’s two-paper format ɑnd helping trainees manage tіmｅ effectively.
Personalized math tuition іn secondary school addresses
private finding ᧐ut gaps in topics like calculus ɑnd statistics, avoiding tһem from hindering О Level success.
Junior college tuition ρrovides access tⲟ supplementary resources ⅼike worksheets and video clip explanations, enhancing Ꭺ Level syllabus protection.
OMT’ѕ custom-made program distinctively sustains tһe MOE curriculum bʏ emphasizing mistake analysis аnd improvement methods
tо lessen blunders іn analyses.
Video explanations ɑrе clеaг and engaging
lor, aiding you grasp complex ideas аnd lift ʏour qualities easily.
Tuition facilities սsе innovative devices ⅼike aesthetic aids, enhancing understanding fߋr much
bｅtter retention in Singapore mathematics exams.
Ⅿү website :: 3rd grade math tutoring online
3rd grade math tutoring online
3 Oct 25 at 7:48 am
It is not my first time to visit this site, i am visiting this web page dailly and obtain nice data
from here all the time.
onewave
3 Oct 25 at 7:48 am
ставки прогнозы [url=www.stavka-12.ru]ставки прогнозы[/url] .
stavka_urSi
3 Oct 25 at 7:49 am
Слив курсов [url=https://sliv.fun/]sliv.fun[/url] .
Sliv kyrsov_leEn
3 Oct 25 at 7:49 am
Очень доволен работой по раскрутке сайта. Исправили технические ошибки, добавили новые разделы и усилили контент. Теперь в Google и Яндекс мы стоим значительно выше, чем раньше https://mihaylov.digital/
Steventob
3 Oct 25 at 7:50 am
прогнозист ру [url=www.stavka-10.ru]www.stavka-10.ru[/url] .
stavka_npSi
3 Oct 25 at 7:50 am
ставки прогнозы на спорт [url=prognozy-na-sport-12.ru]ставки прогнозы на спорт[/url] .
prognozi na sport_akMn
3 Oct 25 at 7:51 am
новости мирового спорта [url=http://novosti-sporta-16.ru]http://novosti-sporta-16.ru[/url] .
novosti sporta_gasi
3 Oct 25 at 7:51 am
свежие новости спорта [url=https://www.novosti-sporta-17.ru]https://www.novosti-sporta-17.ru[/url] .
novosti sporta_xsOi
3 Oct 25 at 7:51 am
ставкипрогнозы [url=www.stavka-12.ru]www.stavka-12.ru[/url] .
stavka_lgSi
3 Oct 25 at 7:52 am
You’ve made some good points there. I looked on the internet for more info about the issue and found most individuals will go along with your views on this web site.
88 AA
3 Oct 25 at 7:52 am
Компания СтройСинтез построила для нас коттедж из кирпича с современным дизайном. Проект был реализован быстро, без задержек и с высоким качеством. Мы довольны на все сто. Больше информации доступно по ссылке – https://stroysyntez.com/
Brianvop
3 Oct 25 at 7:53 am
ставки ру [url=http://stavka-10.ru]http://stavka-10.ru[/url] .
stavka_isSi
3 Oct 25 at 7:54 am
Мы обратились в СтройСинтез для строительства кирпичного дома в Ленинградской области. Работы велись быстро и аккуратно, проект был реализован на высшем уровне. Результат нас полностью устроил. Подробнее можно узнать здесь: https://stroysyntez.com/
Brianvop
3 Oct 25 at 7:55 am
В наше динамичное время, насыщенное напряжением и беспокойством, анксиолитики и транквилизаторы оказались надежным средством для огромного количества людей, позволяя преодолевать панические приступы, генерализованную тревогу и прочие нарушения, мешающие нормальной жизни. Такие медикаменты, включая бензодиазепины (диазепам, алпразолам) или альтернативы без бензодиазепиновой структуры, как буспирон, функционируют за счет повышения влияния ГАМК в головном мозге, уменьшая возбуждение нейронов и обеспечивая быстрое улучшение самочувствия. Особенно полезны они на старте терапии антидепрессантами, когда помогают смягчить начальные побочные эффекты, такие как повышенная раздражительность или бессонница, делая лечение более комфортным и эффективным. Но стоит учитывать возможные опасности: от сонливости и ухудшения внимания до риска привыкания, из-за чего их прописывают на ограниченный период под тщательным медицинским надзором. В клинике “Эмпатия” квалифицированные эксперты, среди которых психиатры и психотерапевты, разрабатывают персонализированные планы, сводя к минимуму противопоказания, такие как нарушения дыхания или беременность. Подробнее о механизмах, применении и безопасном использовании читайте на https://empathycenter.ru/articles/anksiolitiki-i-trankvilizatory/, где собрана вся актуальная информация для вашего спокойствия.
wuwiwef
3 Oct 25 at 7:55 am
Приобрести онлайн кокаин, мефедрон, гашиш, бошки
Jeromeliz
3 Oct 25 at 7:55 am
результаты матчей [url=http://www.novosti-sporta-15.ru]http://www.novosti-sporta-15.ru[/url] .
novosti sporta_cxma
3 Oct 25 at 7:56 am
прогнозы на спорт бесплатные [url=prognozy-na-sport-12.ru]prognozy-na-sport-12.ru[/url] .
prognozi na sport_wzMn
3 Oct 25 at 7:56 am
Мы выбрали кухню с классическим дизайном. Она создаёт уют и гармонично вписалась в интерьер https://kuhni-v-dom.ru/
Eugeniostync
3 Oct 25 at 7:57 am
новости тенниса [url=https://www.novosti-sporta-16.ru]https://www.novosti-sporta-16.ru[/url] .
novosti sporta_ydsi
3 Oct 25 at 7:57 am
спорт онлайн [url=www.novosti-sporta-17.ru/]www.novosti-sporta-17.ru/[/url] .
novosti sporta_qlOi
3 Oct 25 at 7:58 am
I feel this is one of the most significant information for me.
And i’m glad reading your article. But wanna observation on some normal things, The website taste is ideal, the
articles is in point of fact excellent : D.
Just right activity, cheers
Also visit my webpage: retreat center cancun
retreat center cancun
3 Oct 25 at 7:59 am
sliv.fun [url=www.sliv.fun/]www.sliv.fun/[/url] .
Sliv kyrsov_ifEn
3 Oct 25 at 7:59 am
прогнозы на спорт бесплатные [url=www.prognozy-na-sport-12.ru]www.prognozy-na-sport-12.ru[/url] .
prognozi na sport_mpMn
3 Oct 25 at 8:00 am
трактор погрузчик аренда [url=www.arenda-ekskavatora-pogruzchika-cena.ru/]www.arenda-ekskavatora-pogruzchika-cena.ru/[/url] .
arenda ekskavatora pogryzchika cena_svSr
3 Oct 25 at 8:01 am
stavki prognozy [url=http://novosti-sporta-17.ru/]http://novosti-sporta-17.ru/[/url] .
novosti sporta_dbOi
3 Oct 25 at 8:01 am
купить диплом о среднем образовании в реестр [url=https://frei-diplom1.ru/]купить диплом о среднем образовании в реестр[/url] .
Diplomi_fxOi
3 Oct 25 at 8:01 am
Если вы находитесь в поисках качественного портала, то [url=https://rapiershop.ru/]казино 7 к[/url]— прекрасный выбор. Тут обилие автоматов, молниеносные начисления и приятная команда. Однозначно стоит погрузиться!
ThomaswEilt
3 Oct 25 at 8:01 am
Today, I went to the beach with my kids. I found a sea shell and gave it
to my 4 year old daughter and said “You can hear the ocean if you put this to your ear.” She placed
the shell to her ear and screamed. There was a hermit crab
inside and it pinched her ear. She never wants to go back! LoL I know this is totally off topic but I had to
tell someone!
my blog post; News story
News story
3 Oct 25 at 8:01 am
Just swapped USDC for $MTAUR. Vesting worth extending. Project’s potential vast.
minotaurus ico
WilliamPargy
3 Oct 25 at 8:01 am
купить государственный диплом с занесением в реестр [url=https://frei-diplom3.ru]купить государственный диплом с занесением в реестр[/url] .
Diplomi_wuKt
3 Oct 25 at 8:02 am
точные прогнозы на футбол сегодня бесплатно [url=http://prognozy-na-futbol-9.ru]точные прогнозы на футбол сегодня бесплатно[/url] .
prognozi na fytbol_hjea
3 Oct 25 at 8:02 am
Buy Tadalafil online: Generic tadalafil 20mg price – Generic Cialis without a doctor prescription
BruceMaivy
3 Oct 25 at 8:03 am
Foг parents guiding Secondary 1 transitions, secondary school math tuition іs crucial tо track progress іn Singapore’s
fаst-paced classes.
Power lah, оur kids’ math skills рut Singapore at the pinnacle leh!
For parents, progress fuel ᴡith Singapore mah tuition’s enthusiasm.
Secondary math uition іnterest ignites.
Tһrough secondary 1 math tuition, clarity algebraic.
Ϝor visual disabilities, secondary 2 math tuition рrovides audio aids.
Secondary 2 math tuition guarantees ease ⲟf access.
Inclusive secondary 2 math tuition adapts methods.
Secondary 2 math tuition empowers ɑll learners.
The crucial role оf secondary 3 math exams stems fгom
their timing bеfore Օ-Levels, emphasizing mastery.
Ꮋigh marks аllow eco-conscious math tasks. Τhey promote management in peer grߋups.
Singapore’s system optimizes secondary 4 exams smartly. Secondary 4 math tuition algorithms adapt.
Ꭲhiѕ learning improves O-Level. Secondary 4 math tuition smarts.
Math ցoes furtһer than exam preparation; іt’s аn indispensable competency іn thе ᎪӀ era, essential
foг developing ethical аnd efficient AІ solutions.
Mathematical excellence flourishes ԝhen you harbor а love for tһe subject
and consistently apply іts principles tо real-life daily matters.
Οne key іmportance of practicing past math papers fгom multiple Singapore secondary
schools іs gaining familiarity with varying difficulty
levels, preparing f᧐r unexpected challenges in secondary exams.
Uѕing online math tuition е-learning systems aⅼlows
Singapore students t᧐ simulate exam halls virtually fοr realistic practice.
Lah ѕia, Singapore mums ɗon’t worry lor, secondary school teachers experienced, no extra tension.
Ꭺlso visit mʏ blog maths n science tuition in jurong east central
maths n science tuition in jurong east central
3 Oct 25 at 8:03 am
Эта обзорная заметка содержит ключевые моменты и факты по актуальным вопросам. Она поможет читателям быстро ориентироваться в теме и узнать о самых важных аспектах сегодня. Получите краткий курс по современной информации и оставайтесь в курсе событий!
ТОП-5 причин узнать больше – https://library.uog.edu.et/hello-world
LarryProta
3 Oct 25 at 8:03 am
Hey I know this is off topic but I was wondering if you knew of any widgets I could add to my blog that automatically tweet my newest twitter updates.
I’ve been looking for a plug-in like this for quite some time
and was hoping maybe you would have some experience with something like
this. Please let me know if you run into anything. I truly
enjoy reading your blog and I look forward to your new updates.
beruangjitu
3 Oct 25 at 8:03 am
stavkiprognozy ru [url=stavka-10.ru]stavka-10.ru[/url] .
stavka_nzSi
3 Oct 25 at 8:04 am
Слив курсов [url=http://www.sliv.fun]http://www.sliv.fun[/url] .
Sliv kyrsov_kzEn
3 Oct 25 at 8:05 am
DragonMoney – лицензированное казино с щедрыми бонусами, топовыми играми, быстрыми выплатами и круглосуточной поддержкой
драгон казино
EdgarPak
3 Oct 25 at 8:05 am
можно купить диплом медсестры [url=http://frei-diplom15.ru]можно купить диплом медсестры[/url] .
Diplomi_khoi
3 Oct 25 at 8:05 am