Add 'yoast' SEO data to the REST API w/ og & twitter meta fallbacks...

add-yoast-seo-data-to-WP-REST-API.php

<?php
/*
Creates and end-point that get Yoast SEO meta tags...
*/
add_action('rest_api_init', 'add_yoast_data');

function add_yoast_data()
{
    // Add your post types here...
    register_rest_field(array(
        'post',
        'page',
        'directors',
        'project_post_type'
    ), 'yoast', array(
        'get_callback' => 'wp_api_add_yoast_to_post_types',
        'update_callback' => null,
        'schema' => null
    ));
    
    // Public custom post types
    $types = get_post_types(array(
        'public' => true,
        '_builtin' => false
    ));
    foreach ($types as $key => $type) {
        register_rest_field($type, 'yoast', array(
            'get_callback' => 'wp_api_add_yoast_to_post_types',
            'update_callback' => null,
            'schema' => null
        ));
    }
}

function wp_api_add_yoast_to_post_types($post, $field_name, $request)
{
    $postID = $post['id'];
    return return_yoast_array($postID);
}

function return_yoast_array($postID)
{
    $postObject = get_post($postID);
    
    $title         = get_post_meta($postID, '_yoast_wpseo_title', true) ? get_post_meta($postID, '_yoast_wpseo_title', true) : 
        get_the_title($postID);
    $canonical     = get_post_meta($postID, '_yoast_wpseo_canonical', true) ? get_post_meta($postID, '_yoast_wpseo_canonical', true) : 
        get_the_permalink($postID);
    $focus_keyword = get_post_meta($postID, '_yoast_wpseo_focuskw', true); // this is NOT meta-keywords -- Yoast doesn't have that garbage.
    
    $meta_desc = get_post_meta($postID, '_yoast_wpseo_metadesc', true) ? get_post_meta($postID, '_yoast_wpseo_metadesc', true) : 
        (has_excerpt($postID) && trim(get_the_excerpt($postID)) !== "" ? get_the_excerpt($postID) : 
            force_balance_tags(html_entity_decode(wp_trim_words(htmlentities(strip_tags($postObject->post_content)), 50, ""))));
    
    
    /* Opengraph */
    $og_title = get_post_meta($postID, '_yoast_wpseo_opengraph-title', true) ? get_post_meta($postID, '_yoast_wpseo_opengraph-title', true) : 
        $title;
    
    $og_description = get_post_meta($postID, '_yoast_wpseo_opengraph-description', true) ? get_post_meta($postID, '_yoast_wpseo_opengraph-description', true) : 
        $meta_desc;
    
    $og_image = get_post_meta($postID, '_yoast_wpseo_opengraph-image', true) ? get_post_meta($postID, '_yoast_wpseo_opengraph-image', true) : 
        get_the_post_thumbnail_url($postID, 'mediumish-featured-image');
    
    
    /* Twitter */
    $twitter_title = get_post_meta($postID, '_yoast_wpseo_twitter-title', true) ? get_post_meta($postID, '_yoast_wpseo_twitter-title', true) : 
        $title;
    
    $twitter_description = get_post_meta($postID, '_yoast_wpseo_twitter-description', true) ? get_post_meta($postID, '_yoast_wpseo_twitter-description', true) : 
        $meta_desc;
    
    $twitter__image = get_post_meta($postID, '_yoast_wpseo_twitter-image', true) ? get_post_meta($postID, '_yoast_wpseo_twitter-image', true) : 
        get_the_post_thumbnail_url($postID, 'mediumish-featured-image');
    
    /* Return yoast meta to REST API. eg: `route: {content:{yoast:{[FIELDS]}}}` */
    $yoastMeta = array(
        'focuskw' => $focus_keyword,
        'title' => $title,
        'metadesc' => $meta_desc,
        
        'opengraph_title' => $og_title,
        'opengraph_description' => $og_description,
        'opengraph_image' => $og_image,
        'opengraph_updated_time' => get_post_modified_time('U', false, $postID, false), // returns Epoch timestamp
        
        'twitter_title' => $twitter_title,
        'twitter_description' => $twitter_description,
        'twitter_image' => $twitter__image,
        
        'linkdex' => get_post_meta($postID, '_yoast_wpseo_linkdex', true),
        'metakeywords' => get_post_meta($postID, '_yoast_wpseo_metakeywords', true),
        'meta_robots_noindex' => get_post_meta($postID, '_yoast_wpseo_meta-robots-noindex', true),
        'meta_robots_nofollow' => get_post_meta($postID, '_yoast_wpseo_meta-robots-nofollow', true),
        'meta_robots_adv' => get_post_meta($postID, '_yoast_wpseo_meta-robots-adv', true),
        'canonical' => $canonical,
        'redirect' => get_post_meta($postID, '_yoast_wpseo_redirect', true),
        
        'opengraph_url' => get_permalink($postID),
        'opengraph_site_name' => get_bloginfo('name'),
        'opengraph_type' => get_og_type__custom($postObject)
    );
    return (array) $yoastMeta;
}
/* helper funcs */
function get_og_type__custom($postObject)
{
    if (is_front_page() || is_home() || $postObject->post_name == 'homepage') {
        $type = 'website';
    } else {
        $type = 'article';
    }
    return $type;
}
?>