---
Hoa is a modular, extensible and
structured set of PHP libraries.
Moreover, Hoa aims at being a bridge between industrial and research worlds.
# Hoa\Event
[](https://webchat.freenode.net/?channels=#hoaproject)
[](https://gitter.im/hoaproject/central)
[](https://central.hoa-project.net/Documentation/Library/Event)
[](https://waffle.io/hoaproject/event)
This library allows to use events and listeners in PHP. This is an observer
design-pattern implementation.
[Learn more](https://central.hoa-project.net/Documentation/Library/Event).
## Installation
With [Composer](https://getcomposer.org/), to include this library into
your dependencies, you need to
require [`hoa/event`](https://packagist.org/packages/hoa/event):
```sh
$ composer require hoa/event '~1.0'
```
For more installation procedures, please read [the Source
page](https://hoa-project.net/Source.html).
## Testing
Before running the test suites, the development dependencies must be installed:
```sh
$ composer install
```
Then, to run all the test suites:
```sh
$ vendor/bin/hoa test:run
```
For more information, please read the [contributor
guide](https://hoa-project.net/Literature/Contributor/Guide.html).
## Quick usage
We propose a quick overview of how to use events and listeners.
### Events
An event is:
* **Asynchronous** when registering, because the observable may not exist yet
while observers start to observe,
* **Anonymous** when using, because the observable has no idea how many and
what observers are observing,
* It aims at a **large** diffusion of data through isolated components.
Wherever is the observable, we can observe its data.
In Hoa, an event channel has the following form:
`hoa://Event/LibraryName/AnId:pseudo-class#anAnchor`. For instance, the
`hoa://Event/Exception` channel contains all exceptions that have been thrown.
The `hoa://Event/Stream/StreamName:close-before` contains all streams that are
about to close. Thus, the following example will observe all thrown exceptions:
```php
Hoa\Event\Event::getEvent('hoa://Event/Exception')->attach(
function (Hoa\Event\Bucket $bucket) {
var_dump(
$bucket->getSource(),
$bucket->getData()
);
}
);
```
Because `attach` expects a callable and because Hoa's callable implementation is
smart, we can directly attach a stream to an event, like:
```php
Hoa\Event\Event::getEvent('hoa://Event/Exception')->attach(
new Hoa\File\Write('Foo.log')
);
```
This way, all exceptions will be printed on the `Foo.log` file.
### Listeners
Contrary to an event, a listener is:
* **Synchronous** when registering, because the observable must exist before
observers can observe,
* **Identified** when using, because the observable knows how many observers
are observing,
* It aims at a **close** diffusion of data. The observers must have an access
to the observable to observe.
The `Hoa\Event\Listenable` interface requires the `on` method to be present to
register a listener to a listener ID. For instance, the following example
listens the `message` listener ID, i.e. when a message is received by the
WebSocket server, the closure is executed:
```php
$server = new Hoa\Websocket\Server(…);
$server->on('message', function (Hoa\Event\Bucket $bucket) {
var_dump(
$bucket->getSource(),
$bucket->getData()
);
});
```
## Documentation
The
[hack book of `Hoa\Event`](https://central.hoa-project.net/Documentation/Library/Event) contains
detailed information about how to use this library and how it works.
To generate the documentation locally, execute the following commands:
```sh
$ composer require --dev hoa/devtools
$ vendor/bin/hoa devtools:documentation --open
```
More documentation can be found on the project's website:
[hoa-project.net](https://hoa-project.net/).
## Getting help
There are mainly two ways to get help:
* On the [`#hoaproject`](https://webchat.freenode.net/?channels=#hoaproject)
IRC channel,
* On the forum at [users.hoa-project.net](https://users.hoa-project.net).
## Contribution
Do you want to contribute? Thanks! A detailed [contributor
guide](https://hoa-project.net/Literature/Contributor/Guide.html) explains
everything you need to know.
## License
Hoa is under the New BSD License (BSD-3-Clause). Please, see
[`LICENSE`](https://hoa-project.net/LICENSE) for details.