Wordpress wp-json API example using OOP

functions.php

<?php
include_once 'news-api.class.php';
// Implementation Steps:
// Step 1: Call init() in your custom theme or custom plugin code.
$news_api = new News_API();
$news_api->init();

// Step 2: Use the static News_API::get_news_api_posts() method to retrieve the posts in your template file.
$query = new \WP_Query( ['post_type' => 'news', 'posts_per_page' => 5] );
$fetched_news_posts = News_API::get_news_api_posts();

$news_posts = !empty($fetched_news_posts) ?
	array_merge($query->posts, 	$fetched_news_posts) :
	$query->posts ?? [];

news-api.class.php

<?php
class News_API {
	const API_ENDPOINT_PROD = 'https://mattcascardi.info/wp-json';
	const API_ENDPOINT_STG = 'https://matt.issmarterthanyou.com/wp-json';
	const API_SITE_CACHE_KEY = 'news_keywords';
	const API_NEWS_CACHE_KEY = 'news_fmt';
	
	public function init() {
		add_action('wp_head', [$this, 'fetch']);
	}

	public static function get_news_api_posts() {
		return get_transient(self::API_NEWS_CACHE_KEY) ?? [];
	}

	public function fetch() {
		$this->endpoint =  wp_get_environment_type() === 'production' ?
			self::API_ENDPOINT_PROD : self::API_ENDPOINT_STG;

		$result = wp_remote_head( $this->endpoint );

		if ($this->_handle_request_error($result)) {
			return false;
		}

		$url = "{$this->endpoint}/wp/v2/news_keyword";
		$news_endpoint = "{$this->endpoint}/wp/v2/news";

		$this->news_keywords = get_site_transient(self::API_SITE_CACHE_KEY);

		if (! $this->news_keywords ) {
			$this->news_keywords = $this->_do_get_request($url);
			set_site_transient(self::API_SITE_CACHE_KEY, $this->news_keywords, DAY_IN_SECONDS);
			delete_transient(self::API_NEWS_CACHE_KEY);
		}

		foreach( $this->news_keywords as $keyword  ) {
				$news_keyword_id = $keyword->id;
		}

		if (empty($news_keyword_id)) {
			return;
		}

		$news_api_cache_key = self::API_NEWS_CACHE_KEY;
		if ( get_transient( $news_api_cache_key ) ) return;

		$this->news_json = $this->_do_get_request($news_endpoint, ['news_keyword' => $news_keyword_id], true);

        if (empty($this->news_json)) return;

		// Save the representation of the post cards in transient form
		set_transient(
			API_NEWS_CACHE_KEY, $this->get_formatted_news_posts(), DAY_IN_SECONDS
		);
	}

	private function get_formatted_news_posts() {
		$news_api_posts = json_decode($this->news_json);
		$posts = [];

		if (!is_array($news_api_posts) ) {
			return $posts;
		}

		$top_news= array_slice($news_api_posts, 0, 3) ?? [];

		foreach ($top_news as $news_post) {
			$save_post = new \stdClass;
			$save_post->ID = $news_post->id;
			$save_post->card_data = [];
			$save_post->card_data['title'] = $news_post->title->rendered;
			$save_post->card_data['excerpt'] = $news_post->excerpt->rendered;
			$save_post->card_data['link'] = $news_post->link;
			$save_post->card_data['date'] = date('M, j, Y', strtotime($news_post->date));

			// Needs featured image if it has one
			foreach ($news_post->_links as $linkname => $data) {
				if ( 'wp:featuredmedia' === $linkname ) {
					$imageres=$this->_do_get_request($data[0]->href);
					$save_post->card_data['featuredimage'] = $imageres->media_details->sizes->medium->source_url;
				}
			}

			$posts[] = $save_post;
		}

        return $posts;
	}

	private function _do_get_request($endpoint_url, $params = null, $return_json = false) {
		$endpoint_url  .= (!empty($params)) ? '?' . http_build_query($params) : '';
		$result = wp_remote_get($endpoint_url);

		if ($this->_handle_request_error($result)) return null;

		$body = wp_remote_retrieve_body($result);
		return $return_json ?  $body : json_decode( $body ) ;
	}

	/**
	 * Returns true if error
	 * // API Helper
	 *
	 */
	private function _handle_request_error($result) {
		if (!is_array($result)) {
			// It's an error
			error_log(print_r($result->get_error_messages(), true));
			return true;
		}

        if ($result['response']['code'] !== 200) {
			error_log("Error {$result['response']['code']}: {$result['response']['status']} ");
			return true;
		}

		return false;
	}
}