widget classes

/**
 * Add extra "widget-" CSS class to dynamic sidebar widgets. Also adds numeric index class for each widget (widget-1, widget-2, etc.)
based on http://wordpress.org/support/topic/how-to-first-and-last-css-classes-for-sidebar-widgets?replies=9#post-1726957
 */
function widget_first_last_classes($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;
    }

    $class = 'class="widgets-count-' . count($arr_registered_widgets[$this_id]) . ' '; // Add widget count class for additional styling options
    $class .= 'widget-' . $my_widget_num[$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('class="', $class, $params[0]['before_widget']); // Insert our new classes into "before widget"

    return $params;

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