reindex.php

<?php

public function reindex($args, $assoc_args) {
    // Init global index
    $index = $algolia->initIndex('global_search');

    // Clear all objects in the index
    $index->clearObjects()->wait();

    // Get all blog IDs in multisite network
    $all_blog_ids = get_sites(array('fields' => 'ids'));

    // Get all searchable post types
    $searchable_post_types = get_post_types(
        array(
            'public' => true,
            'exclude_from_search' => false
        )
    );

    // Index posts for each site in the multisite network
    foreach ($all_blog_ids as $blog_id) {
        // Switch to the current blog's context
        switch_to_blog($blog_id);
        
        // Loop through searchable post types
        foreach ($searchable_post_types as $post_type) {
          $paged = 1;
          $count = 0;

          do {
              $posts = new WP_Query([
                  'posts_per_page' => 100,
                  'paged' => $paged,
                  'post_type' => $post_type,
                  'post_status' => 'publish',
              ]);

              $records = [];

              // Loop through each post and serialize them
              foreach ($posts->posts as $post) {  
                  // Use post type to get corresponding serializer function
                  $filter_name = $post->post_type.'_to_record';

                  // Serialize and split records
                  $split_records = (array) apply_filters($filter_name, $post);
                  $records = array_merge($records, $split_records);

                  $count++;
              }

              // Save the records in Algolia!
              $index->saveObjects($records);

              WP_CLI::success("$count $post_type records indexed in Algolia");

              $paged++;

          } while (true);

        }
        // Switch back to the current blog's context
        restore_current_blog();
    }
}