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!
mostbet uz ro‘yxatdan qanday o‘tish [url=http://mostbet4182.ru/]http://mostbet4182.ru/[/url]
mostbet_uz_zlkt
18 Oct 25 at 12:41 am
This post will assist the internet people for setting up new
weblog or even a blog from start to end.
Look At This
18 Oct 25 at 12:42 am
лучшие прогнозы на футбол [url=www.prognozy-na-futbol-9.ru/]www.prognozy-na-futbol-9.ru/[/url] .
prognozi na fytbol_cqea
18 Oct 25 at 12:45 am
If you are going for most excellent contents like
myself, only pay a quick visit this site every day since it provides
quality contents, thanks
полировка
18 Oct 25 at 12:45 am
Сегодня мы отправимся на виртуальную экскурсию в уникальные уголки природы России.
Кстати, если вас интересует Изучение ООПТ России: парки, заповедники, водоемы, посмотрите сюда.
Ссылка ниже:
[url=https://alloopt.ru]https://alloopt.ru[/url]
Что думаете о красоте природы России? Делитесь мнениями!
fixRow
18 Oct 25 at 12:46 am
For the reason that the admin of this web page is working,
no doubt very shortly it will be renowned, due to its quality contents.
Prestine glass solutions LLc
18 Oct 25 at 12:46 am
With havin so much content do you ever run into any problems of plagorism or copyright infringement?
My site has a lot of completely unique content I’ve either created myself or outsourced but it looks like a
lot of it is popping it up all over the web without my authorization. Do you know any methods
to help reduce content from being ripped off? I’d truly appreciate it.
https://tw.search.yahoo.com/mobile/s?ei=UTF-8&fl=36&p=site:www.telegramoom.com
18 Oct 25 at 12:47 am
купить диплом в сосновом бору [url=http://rudik-diplom12.ru]http://rudik-diplom12.ru[/url] .
Diplomi_qdPi
18 Oct 25 at 12:47 am
https://telegra.ph/Kupit-binokl-pentaks-voronezhskaya-oblast-avito-10-12-4
JesseHow
18 Oct 25 at 12:58 am
mexican pharmacies that ship: mexico pharmacy – MedicoSur
Andresstold
18 Oct 25 at 12:58 am
регистрация перепланировки [url=https://www.soglasovanie-pereplanirovki-kvartiry3.ru]https://www.soglasovanie-pereplanirovki-kvartiry3.ru[/url] .
soglasovanie pereplanirovki kvartiri _obPi
18 Oct 25 at 1:00 am
https://t.me/s/Official_1xbet_1xbet/1737
Josephadvem
18 Oct 25 at 1:00 am
https://t.me/s/Official_1xbet_1xbet/1642
Josephadvem
18 Oct 25 at 1:01 am
Great beat ! I wish to apprentice while you amend your
web site, how can i subscribe for a blog web site?
The account aided me a acceptable deal. I had been tiny bit acquainted of
this your broadcast offered bright clear idea
Women's sportswear UK
18 Oct 25 at 1:02 am
linebet app download
linebet ????? ?????????
18 Oct 25 at 1:05 am
mostbet uz telegram qo‘llab-quvvatlash [url=https://mostbet4182.ru/]mostbet uz telegram qo‘llab-quvvatlash[/url]
mostbet_uz_aqkt
18 Oct 25 at 1:05 am
https://t.me/s/Official_1xbet_1xbet/1778
Josephadvem
18 Oct 25 at 1:06 am
https://t.me/Official_1xbet_1xbet/1843
Josephadvem
18 Oct 25 at 1:07 am
жб прогнозы на футбол сегодня [url=https://prognozy-na-futbol-9.ru/]prognozy-na-futbol-9.ru[/url] .
prognozi na fytbol_wyea
18 Oct 25 at 1:08 am
проект перепланировки квартиры цена московская область [url=www.proekt-pereplanirovki-kvartiry16.ru]www.proekt-pereplanirovki-kvartiry16.ru[/url] .
proekt pereplanirovki kvartiri_bzMl
18 Oct 25 at 1:14 am
creativityuniverse.shop – I bookmarked a few items, want to come back later for a closer look.
Elton Seryak
18 Oct 25 at 1:15 am
перепланировка помещений [url=https://soglasovanie-pereplanirovki-kvartiry4.ru/]перепланировка помещений[/url] .
soglasovanie pereplanirovki kvartiri _udOr
18 Oct 25 at 1:16 am
I was excited to discover this website. I want to to thank you for
your time for this particularly fantastic read!! I definitely savored every part of it and I
have you book-marked to check out new information on your site.
water heater replacement near me
18 Oct 25 at 1:17 am
cialis: safe online pharmacy for Cialis – tadalafil tablets without prescription
Andresstold
18 Oct 25 at 1:18 am
mostbet karta orqali to‘lov [url=http://mostbet4185.ru]http://mostbet4185.ru[/url]
mostbet_uz_fyer
18 Oct 25 at 1:18 am
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
18 Oct 25 at 1:22 am
Вывод из запоя в стационаре Воронежа — безопасный и эффективный метод лечения. Наши специалисты обеспечат круглосуточное наблюдение и комплексное лечение, включая детоксикацию, восстановление водно-электролитного баланса и психотерапевтическую поддержку.
Получить дополнительную информацию – http://vyvod-iz-zapoya-v-stacionare-voronezh24.ru
Stuartbooms
18 Oct 25 at 1:23 am
точный прогнозы на футбол [url=www.prognozy-na-futbol-9.ru]www.prognozy-na-futbol-9.ru[/url] .
prognozi na fytbol_czea
18 Oct 25 at 1:25 am
https://t.me/s/Official_1xbet_1xbet/1817
Josephadvem
18 Oct 25 at 1:30 am
Somebody necessarily help to make significantly articles I’d state.
This is the very first time I frequented your web page and thus far?
I surprised with the research you made to create this particular submit extraordinary.
Magnificent activity!
https://ru.search.yahoo.com/mobile/s?ei=UTF-8&fl=31&p=site:www.telegramoom.com
18 Oct 25 at 1:30 am
Слив курсов ЕГЭ математика https://courses-ege.ru
courses-ege-345
18 Oct 25 at 1:32 am
проект на перепланировку квартиры цена [url=www.zakazat-proekt-pereplanirovki-kvartiry11.ru]www.zakazat-proekt-pereplanirovki-kvartiry11.ru[/url] .
zakazat proekt pereplanirovki kvartiri_kjet
18 Oct 25 at 1:33 am
мелбет регистрация официальный сайт [url=https://melbetbonusy.ru/]мелбет регистрация официальный сайт[/url] .
melbet_dtOi
18 Oct 25 at 1:33 am
https://www.blurb.com/my/account/profile
https://www.blurb.com/my/account/profile
18 Oct 25 at 1:33 am
вывод из запоя круглосуточно
vivod-iz-zapoya-smolensk022.ru
лечение запоя
vivodzapojsmolenskNeT
18 Oct 25 at 1:33 am
mostbet ilova [url=http://mostbet4185.ru/]mostbet ilova[/url]
mostbet_uz_hver
18 Oct 25 at 1:34 am
https://t.me/Official_1xbet_1xbet/1698
Josephadvem
18 Oct 25 at 1:35 am
https://t.me/s/Official_1xbet_1xbet/1701
Josephadvem
18 Oct 25 at 1:35 am
It’s in fact very difficult in this busy life to
listen news on Television, therefore I only use internet for that purpose,
and obtain the latest information.
найти дизайнера
18 Oct 25 at 1:41 am
I’m gone to say to my little brother, that he should also visit this webpage on regular basis
to obtain updated from newest news.
web page
18 Oct 25 at 1:42 am
ZenCareMeds: safe online medication store – ZenCareMeds
AndrewPal
18 Oct 25 at 1:43 am