MT | TEC | Customized version of the Category Filter that includes CSS classes for subcategories

Tribe__Events__Filterbar__Filters__Category_Custom.php

<?php

/**
 * Customized version of the Category Filter that includes CSS classes for subcategories
 * New filter available in WP-Admin > Events > Settings > Filters
 */
if ( class_exists( 'Tribe__Events__Filterbar__Filters__Category' ) ) {


	class Tribe__Events__Filterbar__Filters__Category_Custom extends Tribe__Events__Filterbar__Filters__Category {

		/**
		 * Flatten out the hierarchical list of event categories into a single list of values,
		 * applying formatting (non-breaking spaces) to help indicate the depth of each nested
		 * item.
		 *
		 * @param array $term_items
		 * @param array $existing_list
		 * @return array
		 */
		protected function flattened_term_list( array $term_items, array $existing_list = null ) {
			// Pull in the existing list when called recursively
			$flat_list = is_array( $existing_list ) ? $existing_list : array();

			// Add each item - including nested items - to the flattened list
			foreach ( $term_items as $term ) {
				$flat_list[] = array(
					'name'  => $term->name,
					'value' => $term->term_id,
					'data'  => array( 'slug' => $term->slug ),
					'class' => 'tribe-events-category-' . $term->slug . ' tribe-events-subcategory-depth-' . $term->depth,
				);

				if ( ! empty( $term->children ) ) {
					$child_items = $this->flattened_term_list( $term->children, $existing_list );
					$flat_list = array_merge( $flat_list, $child_items );
				}
			}

			return $flat_list;
		}

	}
	new Tribe__Events__Filterbar__Filters__Category_Custom( __( 'Category Custom', 'tribe-events-filter-view' ), 'categorycustom' );
}