Adds Bootstrap CSS classes dynamically based on how many widgets in Wordpress Footer

footer.php

<?php
// Add the below to your footer.php file
?>
<footer id="site-footer">
		<div class="container">
			<?php if ( is_active_sidebar('footerfull') ) : ?>
			
			<div id="footer-widgets">
				
				<div class="row">
					
					<?php dynamic_sidebar('Footer'); ?>
					
				</div><!-- end .row -->
			
			</div><!-- end #footer-widgets -->
      
			<?php endif; ?>
  </div>
</footer>

functions.php

<?php
/**
 * Register widget area.
 *
 * @link https://developer.wordpress.org/themes/functionality/sidebars/#registering-a-sidebar
 */
function mwd_widgets_init() {
	register_sidebar( array(
			'name'          => __( 'Footer', 'understrap' ),
			'id'            => 'footerfull',
			'description'   => __( 'Full sized footer widget with dynamic grid', 'text-domain' ),
			'before_widget' => '<div id="%1$s" class="footer-widget %2$s dynamic-classes">',
			'after_widget'  => '</div><!-- .footer-widget -->',
			'before_title'  => '<h3 class="widget-title">',
			'after_title'   => '</h3>',
		)
	);
}
add_action( 'widgets_init', 'mwd_widgets_init' );

// Add Bootstrap column class to widgets
function mwd_widgets_count($params) {
	global $sidebars_widgets;
	
	/*
	 * When the filter runs it checks for changes
	 */
	$sidebars_widgets_count = apply_filters( 'sidebars_widgets', $sidebars_widgets );

	// Only apply changes if sidebar ID is set and the widget's classes depend on the number of widgets in the sidebar.
	if ( isset( $params[0]['id'] ) && strpos( $params[0]['before_widget'], 'dynamic-classes' ) ) {
		$sidebar_id   = $params[0]['id'];
		$widget_count = count( $sidebars_widgets_count[ $sidebar_id ] );

		$widget_classes = 'widget-count-' . $widget_count;
		if ( 0 === $widget_count % 4 || $widget_count > 6 ) {
			// Four widgets per row if there are exactly four or more than six.
			$widget_classes .= ' col-md-3';
		} elseif ( 6 === $widget_count ) {
			// If two widgets are published.
			$widget_classes .= ' col-md-2';
		} elseif ( $widget_count >= 3 ) {
			// Three widgets per row if there's three or more widgets.
			$widget_classes .= ' col-md-4';
		} elseif ( 2 === $widget_count ) {
			// If two widgets are published.
			$widget_classes .= ' col-md-6';
		} elseif ( 1 === $widget_count ) {
			// If just on widget is active.
			$widget_classes .= ' col-md-12';
		}

		// Replace the placeholder class 'dynamic-classes' with the classes stored in $widget_classes.
		$params[0]['before_widget'] = str_replace( 'dynamic-classes', $widget_classes, $params[0]['before_widget'] );
	}

	return $params;

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