static public function isRegistered( $callBack = null, $returnPriority = false )
	{
		if( null === $callBack )
		{
			return self::$_registered;
		}
		if( is_int( $callBack ) )
		{
			return isset( self::$_registeredCallbacks[ $callBack ] ) ? ( $returnPriority ? self::$_registeredCallbacks[ $callBack ][ 1 ] : true ) : false;
		}
		foreach( self::$_registeredCallbacks as $cb )
		{
			if( $cb[ 0 ] === $callBack )
			{
				return $returnPriority ? $cb[ 1 ] : true;
			}
		}
		return false;
	}