function add_options($options, $overwrite = false)
    {

        // continue only if parameter is an array
        if (is_array($options)) {

            // get some properties of the select control
            $attributes = $this->get_attributes(array('options', 'multiple'));

            // if there are no options so far AND
            // we're not overwriting existing options AND
            // the "multiple" attribute is not set
            if (empty($attributes['options']) && $overwrite === false && !isset($attributes['multiple']))

                // add the default value
                // we'll replace the value with the appropriate language
                $options = array('' => $this->form_properties['language']['select']) + $options;

            // set the options attribute of the control
            $this->set_attributes(

				array(

				    'options'   =>  ($overwrite ? $options : $attributes['options'] + $options)

				)

			);

        // if options are not specified as an array
        } else {

            // trigger an error message
            _zebra_form_show_error('
                Selectable values for the <strong>' . $this->attributes['id'] . '</strong> control must be specified as
                an array
            ');

        }

    }