AlgoliaSerializer.php

<?php

class AlgoliaSerializer {
    public function run() {
        add_filter('post_to_record', array($this, 'post_to_record'));
        ...
    }

    // Converts a Post to an Algolia record
    function post_to_record($post) {
        $tags = $this->getTermNames($post, 'post_tag');
        $post_record_attrs = [
            'introduction' => get_field('introduction', $post->ID),
            'tags' => $tags,
        ];
        return $this->serializeRecord($post, $post_record_attrs);
    }

    // Handles formatting record attributes and splitting large content
    function serializeRecord($post, $post_attrs = []) {
        $blog_id = get_current_blog_id();
        $records = [];

        // Split records on post_content
        $records = $this->splitContent('content', $post->post_content);

        // Merge all attributes for each split record and add a unique objectID
        foreach ($records as $key => $split) {
            $records[$key] = array_merge(
                [
                    'objectID' => implode('#', [$blog_id, $post->post_type, $post->ID]),
                    'distinct_key' => implode('#', [$blog_id, $post->post_type, $post->ID]),
                    'blog_id' => $blog_id,
                    'type' => $post->post_type,
                    'title' => $post->post_title,
                    'date' => $post->post_date,
                    'url' => get_permalink($post->ID),
                ],
                $post_attrs,
                $split,
                ['objectID' => implode('-', [$blog_id, $post->post_type, $post->ID, $key])]
            );
        };
        return $records;
    }
}