/**
	 * Singleton
	 * 
	 * @access public static
	 * @return SLS_Security $instance SLS_Security instance
	 * @since 1.0
	 */
	public static function getInstance() 
	{
		if (is_null(self::$_instance)) {
			self::$_instance = new SLS_Security();
		}
		return self::$_instance;
	}