Event driven programming in PHP - Event Class

 
class Event
{
	private $callbacks;
 
	public function Event()
	{
		$this->callbacks = array();
	}
 
	private function Get_Callback($args)
	{
		return (count($args) < 2) ? new Callback($args[0], '') : new Callback($args[1], get_class($args[0]));
	}
 
	public function Subscribe()
	{		
		$callback = $this->Get_Callback(func_get_args());
		if (!in_array($callback, $this->callbacks))
		{		
			$this->callbacks[] = $callback;
		}
		else throw new Exception($callback->method.' already subscribed to this event');
	}
 
	public function Unsubscribe()
	{
		$callback = $this->Get_Callback(func_get_args());
		$key = array_search($callback, $this->callbacks);		
		if (!($key === false))
		{
			unset($this->callbacks[$key]);
		}
		else throw new Exception($callback->method.' not subscribed to this event');		
	}
 
	public function Raise()
	{
		foreach($this->callbacks as $callback)
		{
			if (method_exists($callback->context, $callback->method) || function_exists($callback->method))
			{				
				$params = func_get_args();
				$callback = (!empty($callback->context)) ? array($callback->context, $callback->method) : $callback->method;
				call_user_func_array($callback, $params);
			}
			else throw new Exception($callback->method." does not exist");
		}
	}
}
 

 
class Callback
{
    public $method;
    public $context;
 
    public function Callback($method, $context)
    {
        $this->method = $method;
        $this->context = $context;
    }
}