WordPress hook that loops through widget areas and add some custom classes for each one of them

wp-widget-foundation-custom-classes.php

<?php
/**
 * Loop through widget areas and add custom classes for each one of them
 *
 * @link http://colourstheme.com/2015/03/add-class-to-first-and-last-widget/ Reference #1
 * @link https://gist.github.com/slobodan/6156076 Reference #2
 */
function fltnt_add_widget_custom_classes() {
    global $wp_registered_widgets;

    // Find those widgets
    $sidebars = wp_get_sidebars_widgets();

    if ( empty ( $sidebars ) ) {
        return;
    }

    // Loop through each widget area
    foreach ( $sidebars as $sidebar_id => $widgets ) {

        // Our main sidebar doesn't need additional classes
        if ( 'sidebar-main' == $sidebar_id ) {
            continue;
        }

        // Get the number of widgets on the sidebar
        $number_of_widgets = count( $widgets );

        foreach ( $widgets as $i => $widget_id ) {

            $widget_classes = '';
            $widget_position = ( $i + 1 );

            // Add a class for widget position
            $widget_classes .= ' widget-position-' . $widget_position;

            // Add a class for the total number of widgets in this widget area
            $widget_classes .= ' widget-count-' . $number_of_widgets;

            // Add first widget class
            if ( 1 == $widget_position ) {
                $widget_classes .= ' widget-first';
            }

            // Add last widget class
            if ( $number_of_widgets == $widget_position ) {
                $widget_classes .= ' widget-last';
            }

            // Add specific Foundation classes for layouts with, respectively, 6, 4, 3 or 2 columns
            if ( 6 == $number_of_widgets ) {
                $widget_classes .= ' medium-2';
            }
            elseif ( 4 == $number_of_widgets ) {
                $widget_classes .= ' medium-3';
            }
            elseif ( 3 == $number_of_widgets ) {
                $widget_classes .= ' medium-4';
            }
            elseif ( 2 == $number_of_widgets ) {
                $widget_classes .= ' medium-6';
            }
            else {
                $widget_classes .= ' medium-12';
            }

            // Add Foundation columns
            $widget_classes .= ' columns';

            // Save new classes into global $wp_registered_widgets
            $wp_registered_widgets[$widget_id]['classname'] .= $widget_classes;
        }
    }
}
add_action( 'init', 'fltnt_add_widget_custom_classes' );

nice

Great! Exactly what I was searching, thank you.