WordPress Rest API. Add post terms with labels to API response

rest-api-terms-with-labels.php

<?php
/**
 * Add this code without opening PHP tag into funcitons.php og your active theme or with any code snippets plugin
 */
add_action(
	'rest_api_init',
	function() {

		/**
		 * Here you can set taxonomies slugs you wnat to add to Rest API response
		 * Expected format:
		 * 
		 * array(
		 *     'post_type_1_slug' => array( 'tax_1_slug_for_cpt_1', 'tax_2_slug_for_cpt_1', ... ),
		 *     'post_type_2_slug' => array( 'tax_1_slug_for_cpt_2', 'tax_2_slug_for_cpt_1', ... ),
		 * )
		 * 
		 */
		$taxonomies_to_register = array(
			'post'  => array( 'category', 'post_tag' ),
			'tours' => array( 'tour_type' ),
		);

		foreach ( $taxonomies_to_register as $post_type => $taxes ) {
			foreach ( $taxes as $tax ) {
				register_rest_field(
					$post_type,
					$tax . '_with_labels',
					array(
						'get_callback' => function( $object ) use ( $tax ) {
							$terms = wp_get_post_terms( $object['id'], $tax, array( 'fields' => 'id=>name' ) );
							if ( empty( $terms ) ) {
								return array();
							} else {
								$result = array();

								foreach ( $terms as $id => $label ) {
									$result[] = array(
										'id'    => $id,
										'label' => $label,
									);
								}

								return $result;
							}
						},
						'schema' => array(
							'type'  => 'array',
							'items' => array(
								'type'       => 'object',
								'properties' => array(
									'id' => array(
										'type' => 'integer',
									),
									'label' => array(
										'type' => 'string',
									),
								),
							),
						)
					)
				);
			}
		}

	}
);