Event(NodeJs style) class for PHP

Event.php

/**
 * Created by IntelliJ IDEA.
 * User: hongbo
 * Date: 4/26/12
 * Time: 9:59 AM
 */

class Event
{

    protected $events = array();

    public function emit($event, $args = array())
    {
        if(isset($this->events[$event]))
        {
            foreach($this->events[$event] as $func)
            {
                call_user_func($func, $args);
            }
        }
    }

    public function on($event, Closure $func)
    {
        if(!isset($this->events[$event])){
            $this->events[$event] = array();
        }
        $this->events[$event][] = $func;
        $idx = array_push($this->events[$event],$func) -1;
        $self = $this;
        return function() use($idx,$event,&$self){
            array_splice($self->events[$event],$idx,1);
            return $self;
        };
    }

    public function once($event,Closure $func){
        if(!isset($this->events[$event])){
            $this->events[$event] = array();
        }
        $idx = count($this->events[$event]);
        $self = $this;
        $_func =  function($args) use(&$func,$idx,$event,&$self){
            call_user_func($func, $args);
            array_splice($self->events[$event],$idx,1);
        };
        array_push($self->events[$event],$_func);
    }

    public function off($event, Closure $func)
    {
        if(!isset($this->events[$event])){
            return;
        }
        $this->events[$event] = array_filter($this->events[$event],function($item) use ($func){
            return $item == $func;
        });
    }

}