phly-event-emitter

Experimental!

This library is experimental, tracking different iterations and experiments being proposed for PSR-14. It is highly unstable in terms of API; use at your own risk.

This library provides an implementation of the following proposed PSR-14 interfaces:

• ListenerProvider implements ListenerProviderInterface, and allows you to attach listeners to any message type. It then acts as a generator, looping through each listener and testing if it handles the message type.

• PrioritizedListenerProvider also implements ListenerProviderInterface, and allows you to attach listeners to any message type, with an integer priority. When listeners are retrieved, it loops through all attached listeners, and injects those capable of listening to the emitted message to a priority queue, which it then returns.

• MessageNotifier implements MessageNotifierInterface, and accepts a ListenerProviderInterface to its constructor. It then loops through and notifies listeners returned for the message. If any listeners throw exceptions, it catches them, and, when all listeners have been notified, throws a Phly\EventEmitter\Exception\ExceptionAggregate that aggregates all of them; call the getListenerExceptions() method of that class to iterate through them.

• TaskProcessor implements TaskProcessorInterface, and accepts a ListenerProviderInterface to its constructor. It then loops through and processes listeners returned for the task, halting early if the task is stoppable and indicates propagation has been stopped. Exceptions thrown by listeners are not caught.

It DOES NOT provide implementations for the following interfaces:

• EventInterface (consumers will create these)
• MessageInterface (consumers will create these)
• TaskInterface (consumers will create these)
• StoppableTaskInterface (consumers will create these)

Installation

You will first need to add a repository entry to your composer.json:

"repositories": [
    {
        "type": "vcs",
        "url": "https://github.com/phly/phly-event-emitter.git"
    }
],

Then, run the following to install this library:

$ composer require phly/phly-event-emitter

Documentation

Basic usage

The following demonstrates using the ListenerProvider to attach a listener. The provider is then used to seed either a MessageNotifier or TaskProcessor.

use Phly\EventEmitter\MessageNotifier;
use Phly\EventEmitter\ListenerProvider;

$listeners = new ListenerProvider();
$listeners->on(BootstrapEvent::class, function ($e) {
    // do something with the bootstrap event
});

$notifier = new MessageNotifier($listeners);
$notifier->notify(new BootstrapEvent($params));

Prioritized listeners

The following example uses a PrioritizedListenerProvider to provide three different listeners, each with a different priority. Priorities are integers; higher priorities execute first, while lower priorities (including negative priorities) execute last.

use Phly\EventEmitter\TaskProcessor;
use Phly\EventEmitter\PrioritizedListenerProvider;

$listeners = new PrioritizedListenerProvider();
$listeners->on(BootstrapTask::class, function ($e) {
    echo 1, PHP_EOL;
}, -100);
$listeners->on(BootstrapTask::class, function ($e) {
    echo 2, PHP_EOL;
}, 100);
$listeners->on(BootstrapTask::class, function ($e) {
    echo 3, PHP_EOL;
}, 1);

$processor = new TaskProcessor($listeners);
$processor->process(new BootstrapTask($params));

In the above, the output will become:

2
3
1

Support

• Issues