Import to WordPress from JSON

data.json

{
   "0":{
      "slug":"lorem-ipsum",
      "title":"Lorem Ipsum",
      "publish_date":"2018-10-12T05:00:00.000Z",
      "featured_image":"https://link.to/image.jpg",
      "content":"Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque blandit tempus feugiat. Nullam purus massa, ultricies vel erat ac, tempor condimentum lorem. Etiam malesuada egestas tincidunt.",
      "page_title":"Welcome to Lorem Ipsum",
      "description":"Nulla sit amet massa fringilla eros tempor tempus. Fusce auctor arcu sed ipsum eleifend, sit amet tincidunt ligula porta."
   }
}

wp-json-import.php

<?php

namespace App;
global $sage_error;

add_action('after_setup_theme', function () use ($sage_error) {
    if (! file_exists($data = __DIR__.'/data.json')) {
        return $sage_error("{$data} could not be found.");
    }

    $data = json_decode(file_get_contents($data));

    return collect($data)
        ->filter()
        ->flatMap(function ($post) {
            if (get_page_by_title($post->title, 'OBJECT', 'post') || empty($post->content)) {
                return;
            }

            $post->id = wp_insert_post([
                'post_title'   => $post->title,
                'post_name'    => $post->slug,
                'post_date'    => $post->publish_date,
                'post_content' => collect($post->content)->implode(''),
                'post_author'  => 1,
                'post_status'  => 'publish',
                'meta_input'   => [
                    '_yoast_wpseo_title'    => $post->page_title,
                    '_yoast_wpseo_metadesc' => $post->description ?? null
                ]
            ], true);

            if (! is_wp_error($post->id) && ! empty($post->featured_image)) {
                collect(['media', 'file', 'image'])
                    ->map(function ($file) {
                        require_once(ABSPATH."wp-admin/includes/{$file}.php");
                    });

                if ($post->featured_image = media_sideload_image($post->featured_image, $post->id, $post->title, 'id')) {
                    set_post_thumbnail($post->id, $post->featured_image);
                }
            }

            return;
        });
}, 20);