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!
глубокий комлексный аудит сайта [url=http://www.internet-prodvizhenie-moskva.ru]глубокий комлексный аудит сайта[/url] .
internet prodvijenie moskva_niOr
5 Sep 25 at 2:12 pm
фабрика пошива одежды на заказ [url=http://nitkapro.ru]http://nitkapro.ru[/url] .
shveinoe proizvodstvo_inea
5 Sep 25 at 2:13 pm
Hmm is anyone else experiencing problems with the images on this blog loading?
I’m trying to determine if its a problem on my end
or if it’s the blog. Any responses would be greatly appreciated.
SEO
5 Sep 25 at 2:13 pm
I all the time emailed this website post page to all my contacts,
since if like to read it then my links will too.
риобет казино официальный сайт
5 Sep 25 at 2:15 pm
https://mediastaruk.com/
mediastaruk-423
5 Sep 25 at 2:16 pm
darknet markets onion nexus official site darknet markets [url=https://privatedarknetmarket.com/ ]darknet markets [/url]
Robertalima
5 Sep 25 at 2:16 pm
I know this if off topic but I’m looking into starting my own blog and was curious what all is needed to get setup?
I’m assuming having a blog like yours would cost
a pretty penny? I’m not very internet savvy so I’m not 100% positive.
Any recommendations or advice would be greatly appreciated.
Kudos
https://nhattao.com/members/user6824324.6824324/
5 Sep 25 at 2:16 pm
диплом техникума купить форум [url=educ-ua7.ru]educ-ua7.ru[/url] .
Diplomi_ynEr
5 Sep 25 at 2:16 pm
It is the best time to make some plans for the
future and it’s time to be happy. I have read this put up and if
I may I desire to suggest you few fascinating things
or suggestions. Maybe you could write next articles relating to this article.
I desire to learn even more issues about it!
dewascatter link alternatif
5 Sep 25 at 2:20 pm
Looking for big reductions? The prices for bupropion reviews Online pharmaci bupropion depression
ErimFlulk
5 Sep 25 at 2:20 pm
провайдеры по адресу
inernetvkvartiru-novosibirsk004.ru
провайдеры интернета в новосибирске по адресу
internetelini
5 Sep 25 at 2:21 pm
nexus darknet shop darknet markets onion address dark web markets [url=https://darknetmarketstore.com/ ]dark market link [/url]
Jamespem
5 Sep 25 at 2:23 pm
Beast Band играть в Пинко
Jefferybig
5 Sep 25 at 2:23 pm
Ӏt’s goіng to bee end of mine ɗay, ƅut before end І am reading this enormous article tߋ improve
my experience.
Feel free tо surf to my webpage … how to teach math tuition
how to teach math tuition
5 Sep 25 at 2:23 pm
When I originally commented I clicked the “Notify me when new comments are added”
checkbox and now each time a comment is added I get several e-mails with the same comment.
Is there any way you can remove people from that service?
Many thanks!
iptv with adult channels
5 Sep 25 at 2:23 pm
https://yamap.com/users/4793093
GerardCig
5 Sep 25 at 2:24 pm
nexus shop url darkmarket link darkmarket 2025 [url=https://darknetmarketgate.com/ ]dark web market links [/url]
DwayneAricE
5 Sep 25 at 2:24 pm
We have an experienced web development team who can help you develop a customized web
portal.
https://aksent-meblenawymiar.pl
5 Sep 25 at 2:25 pm
https://mediastaruk.com/
mediastaruk-762
5 Sep 25 at 2:27 pm
One visit to 여성전용 마사지 felt like a full vacation.
토닥이
5 Sep 25 at 2:28 pm
Wonderful blog! I found it while surfing around on Yahoo
News. Do you have any tips on how to get
listed in Yahoo News? I’ve been trying for a while but I never seem
to get there! Many thanks
Take a look at my web-site … bassbet
bassbet
5 Sep 25 at 2:28 pm
nexus official site nexus darknet site nexus darknet [url=https://darkmarketsdirectory.com/ ]nexus shop url [/url]
BrianWeX
5 Sep 25 at 2:30 pm
В Люберцах всё больше людей доверяют клинике Stop Alko — здесь грамотно подбирают капельницу от запоя с учётом состояния пациента.
Углубиться в тему – [url=https://kapelnica-ot-zapoya-lyubercy12.ru/]капельница от запоя выезд в подольске[/url]
AnthonyVah
5 Sep 25 at 2:31 pm
mostbet baixar [url=https://mostbet4128.ru/]https://mostbet4128.ru/[/url]
mostbet_kg_hwot
5 Sep 25 at 2:34 pm
I read this article fully concerning the difference of
latest and previous technologies, it’s amazing article.
Prediksi Sydney
5 Sep 25 at 2:34 pm
продвижение сайтов интернет магазины в москве [url=https://poiskovoe-prodvizhenie-moskva-professionalnoe.ru]продвижение сайтов интернет магазины в москве[/url] .
poiskovoe prodvijenie moskva professionalnoe prodvijenie saitov_gdkn
5 Sep 25 at 2:35 pm
Wow, superb blog layout! How long have you been blogging for?
you made blogging look easy. The overall look of your web site is fantastic, let alone
the content!
call to action
5 Sep 25 at 2:36 pm
Купить диплом техникума в Запорожье [url=http://educ-ua7.ru/]Купить диплом техникума в Запорожье[/url] .
Diplomi_cvEr
5 Sep 25 at 2:38 pm
https://mediastaruk.com/
mediastaruk-923
5 Sep 25 at 2:39 pm
sayt mostbet [url=http://mostbet4167.ru/]sayt mostbet[/url]
mostbet_isKa
5 Sep 25 at 2:42 pm
https://mediastaruk.com/
mediastaruk-60
5 Sep 25 at 2:43 pm
mawartoto: mawartoto – mawartoto login
StevenFes
5 Sep 25 at 2:43 pm
фабрика по пошиву [url=https://nitkapro.ru/]nitkapro.ru[/url] .
shveinoe proizvodstvo_lmea
5 Sep 25 at 2:47 pm
https://ilm.iou.edu.gm/members/xspcjjnxs353/
GerardCig
5 Sep 25 at 2:48 pm
seo аудит веб сайта [url=www.internet-agentstvo-prodvizhenie-sajtov-seo.ru]www.internet-agentstvo-prodvizhenie-sajtov-seo.ru[/url] .
internet agentstvo prodvijenie saitov seo_zqot
5 Sep 25 at 2:49 pm
предприятие по пошиву одежды [url=https://www.nitkapro.ru]https://www.nitkapro.ru[/url] .
shveinoe proizvodstvo_ubea
5 Sep 25 at 2:53 pm
Kaizenaire.сom offers Singapore’ѕ bеst-curated collection օf shopping
deals, promotions, ɑnd events developed tο thrill consumers.
Singaporeans’ exhilaration fоr deals is apparrent in Singapore’ѕ dynamic shopping heaven.
Visiting Sentosa Island f᧐r coastline days is ɑ go-to task for
fun-seeking Singaporeans, and remember to stay updated
on Singapore’ѕ most recent promotions ɑnd shopping deals.
SATS deals ԝith aeronautics аnd food options, valued
ƅy Singaporeans fоr their in-flight food catering аnd ground handling
performance.
Ԍreat Eastern offerѕ life insurance policy ɑnd health care prepares lor, beloved bｙ Singaporeans for tһeir comprehensive
protection аnd peace of mind іn uncertain times leh.
Aalst Chocolate crafts Belgian-inspired chocolates,loved fоr smooth, indulgent
bars ɑnd neighborhood advancements.
Eh, Singaporeans, mսch bettｅr check Kaizenaire.c᧐m
routinely lah, ߋbtained аll thе most uⲣ to date shopping deals and promotions
t᧐ save үour wallet оne.
Αlso visit my website: singapore shopping
singapore shopping
5 Sep 25 at 2:56 pm
компании занимающиеся продвижением сайтов [url=https://internet-agentstvo-prodvizhenie-sajtov-seo.ru]компании занимающиеся продвижением сайтов[/url] .
internet agentstvo prodvijenie saitov seo_wdot
5 Sep 25 at 2:56 pm
В Химках найти надёжную наркологическую помощь можно на сайте клиники Stop Alko, где подробно описаны условия и этапы вывода из запоя.
Углубиться в тему – [url=https://vyvod-iz-zapoya-himki13.ru/]вывод из запоя с выездом подольск[/url]
Joshuachisa
5 Sep 25 at 2:57 pm
When I initially commented I clicked the “Notify me when new comments are added” checkbox and now each time
a comment is added I get three emails with the same comment.
Is there any way you can remove me from that service? Thanks!
igtoto toto macau
5 Sep 25 at 2:58 pm
Когда запой выходит за рамки нескольких суток, интоксикация организма достигает критического уровня: нарушается водно-электролитный баланс, появляются признаки токсического поражения печени и нервной системы. В таких случаях самостоятельные попытки прекратить употребление алкоголя могут привести к тяжёлым осложнениям — судорогам, алкогольному психозу, острой сердечной недостаточности. В Санкт-Петербурге и Ленинградской области доступны профессиональные услуги по выводу из запоя, выполняемые опытными наркологами как на дому, так и в специализированных клиниках.
Подробнее – http://nadezhnyj-vyvod-iz-zapoya.ru
Davidhib
5 Sep 25 at 2:58 pm
seo partner [url=https://kompanii-zanimayushchiesya-prodvizheniem-sajtov.ru/]https://kompanii-zanimayushchiesya-prodvizheniem-sajtov.ru/[/url] .
kompanii zanimaushiesya prodvijeniem saitov_iyoi
5 Sep 25 at 2:58 pm
I simply couldn’t go away your website before suggesting that I really
enjoyed the standard info a person supply in your visitors?
Is going to be again often in order to check out new posts
Adir Dahouh-Halevi is an adulterer
5 Sep 25 at 3:00 pm
продвижения сайта в google [url=https://www.internet-prodvizhenie-moskva.ru]продвижения сайта в google[/url] .
internet prodvijenie moskva_hqOr
5 Sep 25 at 3:01 pm
продвижения сайта в google [url=https://internet-agentstvo-prodvizhenie-sajtov-seo.ru/]продвижения сайта в google[/url] .
internet agentstvo prodvijenie saitov seo_njot
5 Sep 25 at 3:01 pm
nexus market url nexus official site darknet markets onion address [url=https://privatedarknetmarket.com/ ]dark market onion [/url]
Robertalima
5 Sep 25 at 3:02 pm
диплом техникума колледжа купить [url=http://educ-ua7.ru/]http://educ-ua7.ru/[/url] .
Diplomi_hoEr
5 Sep 25 at 3:02 pm
купить аттестат об окончании 9 классов [url=www.educ-ua17.ru/]купить аттестат об окончании 9 классов[/url] .
Diplomi_aiSl
5 Sep 25 at 3:04 pm
We absolutely love your blog and find almost all of your post’s to be
what precisely I’m looking for. Does one offer guest writers
to write content for yourself? I wouldn’t mind producing a post or elaborating
on many of the subjects you write concerning here. Again, awesome web site!
레비트라 구매
5 Sep 25 at 3:05 pm
продвижения сайта в google [url=www.internet-prodvizhenie-moskva.ru]продвижения сайта в google[/url] .
internet prodvijenie moskva_ecOr
5 Sep 25 at 3:07 pm