Increase widget with 1

I found the solution exactly what i was looking for

https://wordpress.org/support/topic/how-to-first-and-last-css-classes-for-sidebar-widgets?replies=9

Just in case someone might need to add CSS3 animations like this http://jackonthe.net/css3animateit

here is the hook to create Data id’s for each widget

/**
 * Add data Id for CSS3 animate plugin
 */
function CSS3_Data_ID($params) {

	global $my_widget_num; // Global a counter array

	$this_id = $params[0]['id']; // Get the id for the current sidebar we're processing

	$arr_registered_widgets = wp_get_sidebars_widgets(); // Get an array of ALL registered widgets	

	if(!$my_widget_num) {// If the counter array doesn't exist, create it
		$my_widget_num = array();
	}

	if(!isset($arr_registered_widgets[$this_id]) || !is_array($arr_registered_widgets[$this_id])) { // Check if the current sidebar has no widgets
		return $params; // No widgets in this sidebar... bail early.
	}

	if(isset($my_widget_num[$this_id])) { // See if the counter array has an entry for this sidebar
		$my_widget_num[$this_id] ++;
	} else { // If not, create it starting with 1
		$my_widget_num[$this_id] = 1;
	}

	$data_id = 'data-id="' . $my_widget_num[$this_id] . ''; // Add a widget number class for additional styling options

	/* if($my_widget_num[$this_id] == 1) { // If this is the first widget
		$class .= 'widget-first ';
	} elseif($my_widget_num[$this_id] == count($arr_registered_widgets[$this_id])) { // If this is the last widget
		$class .= 'widget-last ';
	} */

	$params[0]['before_widget'] = str_replace('data-id="', $data_id, $params[0]['before_widget']); // Insert our new classes into "before widget"

	return $params;

}
add_filter('dynamic_sidebar_params','CSS3_Data_ID');