Changes to methods in class-common.php to add Post Thumbnail to the Advanced Search cache

class-common.php

<?php
	/**
	 * Register the JavaScript for the public-facing side of the site.
	 *
	 * @since    1.0.0
	 */
	public function enqueue_scripts() {

		$transient_name = $this->plugin_transients['autosuggest_transient'];
		$cached_posts_titles = array();
		$cached_posts_data = array();

		// check if cached posts are available, and make the data available to the JavaScript.
		$cached_posts = get_transient( $transient_name );
		// $cached_posts will contain an object with Post ID, Title and the Thumbnail URI.
		
		if ( $cached_posts ) {
			foreach ( $cached_posts as $index => $post ) {
				$cached_posts_titles[ $index ] = $post['title'];
				$cached_posts_data[$index] = array(
					'id' => $post['id'],
					'title' => $post['title'],
					'thumbnail_uri' => $post['post_thumbnail_uri'],
				);
			}
		}

		$params = array(
			'ajaxurl' => admin_url( 'admin-ajax.php' ),
			'cached_post_titles' => $cached_posts_titles,
			'cached_posts_data' => $cached_posts_data, // make the cached posts data available in the JavaScript.
		);
		wp_enqueue_script( 'nds_advanced_search', plugin_dir_url( __FILE__ ) . 'js/nds-advanced-search.js', array( 'jquery', 'jquery-ui-autocomplete' ), $this->version, true );
		wp_localize_script( 'nds_advanced_search', 'params', $params );

	}

 /**
	 * Cache WordPress posts for post types that are specified in the
	 * plugin setting to be included in the custom search.
	 *
	 * @since 1.0.0
	 */
	public function cache_posts_in_post_types() {
		$transient_name = $this->plugin_transients['autosuggest_transient'];
		$transient_expiration = $this->plugin_transients['autosuggest_transient_expiration'];

		// retrieve the selected post types from the plugin settings to include in the custom search.
		$plugin_options = get_option( $this->plugin_name );
		$post_types = array_keys( $plugin_options, 1, true );

		// check the transient for existing cached data.
		$cached_posts = get_transient( $transient_name );
		if ( false === $cached_posts ) {
			$args = array(
				'post_type'           => $post_types,
				'post_status'         => 'publish',
				'posts_per_page'      => -1,
				'no_found_rows'       => true, // true by default.
				'suppress_filters'    => false, // true by default.
				'ignore_sticky_posts' => true, // true by default.
			);

			// get_posts() to retrieve posts belonging to the required post types.
			$posts_in_required_post_types = get_posts( $args );

			// Check if posts were found.
			if ( $posts_in_required_post_types ) {
				foreach ( $posts_in_required_post_types as $key => $post ) {

					// get the URL for featured image.
					$featured_img_url = get_the_post_thumbnail_url( $post->ID );

					// cache the post titles, post ids, and the image url.
					$cached_post = array(
						'id' => $post->ID,
						'title' => esc_html( $post->post_title ),
						'post_thumbnail_uri' => $featured_img_url ? esc_html( $featured_img_url ) : false,
					);
					$cached_posts[] = $cached_post;
				}

				/**
				 * Save the post data in a transient.
				 * For better performance cache only the post ids, titles
				 * instead of the entire WP Query.
				 */
				set_transient( $transient_name, $cached_posts, $transient_expiration );
			}
		}
		return $cached_posts;
	}

 /**
	 * AJAX handler for the auto-suggest.
	 *
	 * Callback for the "wp_ajax_nds_advanced_search_autosuggest" and
	 * "wp_ajax_nopriv_nds_advanced_search_autosuggest" hooks in "class-init.php"
	 *
	 * @since    1.0.0
	 */
	public function advanced_search_autosuggest_handler() {

		$transient_name = $this->plugin_transients['autosuggest_transient'];

		// check if cached posts are available.
		$cached_posts = get_transient( $transient_name );
		if ( false === $cached_posts ) {

			// retrieve posts by running a new query and cache the posts in the transient as well.
			$cached_posts = $this->cache_posts_in_post_types();
		}

		$cached_post_titles = array();
		$cached_posts_data = array();

		foreach ( $cached_posts as $index => $post ) {
			$cached_post_titles[ $index ] = $post['title'];
			$cached_posts_data[$index] = array(
				'id' => $post['id'],
				'title' => $post['title'],
				'thumbnail_uri' => $post['post_thumbnail_uri'], // also pass in the post_thumbnail_uri
			);
		}

		// Echo the response to the AJAX request.
		// the response is the $cached_posts_data object which contains titles as well as post thumbail.

		// wp_send_json( $cached_post_titles ); // Note: earlier this was an array
		wp_send_json( $cached_posts_data ); // Note: this is an object.

		// wp_send_json will also die().
	}