Shimmie2 / SCore
An event is a little blob of data saying "something happened", possibly "something happened, here's the specific data".
Events are sent with the send_event() function. Since events can store data, they can be used to return data to the extension which sent them, for example:
$tfe = new TextFormattingEvent($original_text); send_event($tfe); $formatted_text = $tfe->formatted;
An extension is something which is capable of reacting to events.