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We used the observer pattern to write our own EventObserver, which enables us to use Event Driven Development in an Agavi project.

Since we are working module-based, there are two simple steps to add an Event listener for your module to the system.

1. Add %module_dir%/config/event_listeners.xml

<?xml version="1.0" encoding="UTF-8"?>
<config>
    <listeners>
        <event>
            <name>modules.forum.post.new</name>
            <callback>Forum_DefaultListener</callback>
        </event>
    </listeners>
</config>

The <name> element holds the event name or “channel”, the <callback> element holds the name of the listener-class.

2. Add %module_dir%/listeners/Forum_DefaultListener.class.php

(Note: callback name goes here as you can see, for autoloading)

class Forum_DefaultListener implements EventListenerInterface
{
    public static function listenToEvent(Event $event) {
        $name = $event->getName();
        switch($name) {
            case 'modules.forum.post.new':
                throw new HelloWorldException();
        }
    }
}

Listening to ‘modules.forum.post.new’ events is working from this point

Firing events is as easy as this, anywhere in your module-code:

EventObserver::getInstance()
    ->notify(new Event('modules.forum.post.new', $message));

This call will find its way to the configured listener, Forum_DefaultListener, and Forum_DefaultListener::listenToEvent (like any other listener) will be called with an Event, including the passed $message object.

Related posts:

1. Agavi vs Zend Framework Part 1 – Forms