I am storing data from an API in a custom post type made up with Advanced Custom Field. The API returns image urls, where each is given a text field in Advanced Custom Field. I'd like to set a specific of those as the featured image of the post type.

I found a few ways of doing it, if the image was a imagefield or galleryfield, but since it's just a URL for now, I am struggling with it.

So the question is boiled down to; how would I set a featured image from a given URL from a 3rd party?

Any advice would be appreciated.

Some code from functions.php

// Setting Costum Post Type
add_action('init', 'register_cars');
function register_cars(){
    register_post_type('car', [
        'label' => 'Cars',
        'public' => true,
        'capability_type' => 'post',
        'publicly_queryable' => true,
        'show_ui'            => true,
        'hierarchical'       => true,
        'has_archive'        => true,
        'rewrite'            => array('slug' => 'car', 'with_front' => false),
        'supports'           => array('title', 'editor', 'thumbnail'),
        'menu_position'      => 31
    ]);
}

// Getting the cars from our API
function get_cars_from_api() {
    
    // Call the API and get a response 
    $url = "URL_HERE";

    $curl = curl_init($url);
    curl_setopt($curl, CURLOPT_URL, $url);
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);

    $headers = array(
       "Authorization: Basic AUTH_HERE",
    );
    curl_setopt($curl, CURLOPT_HTTPHEADER, $headers);
    
    // For debug
    curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, false);
    curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
    
    // Decode our response to json
    $resp = curl_exec($curl);
    curl_close($curl);
    $arr = json_decode($resp, true);
    $cars[] = $arr;
    
    // Loop through our response
    foreach($arr['Vehicles'] as $car) {
        $car_slug = sanitize_title($car['Make'] . ' ' . $car['Model'] . ' ' . $car['Variant'] . ' (ID: ' . $car['VehicleId'] . ')');
        $car_name = $car['Make'] . ' ' . $car['Model'] . ' ' . $car['Variant'] . ' (ID: ' . $car['VehicleId'] . ')';
        $existing_car = get_page_by_path($car_slug, 'OBJECT', 'car');

        // Check if we need to create or update the car
        if($existing_car === null) {
            $inserted_car = wp_insert_post([
                'post_name' => $car_slug,
                'post_title' => $car_name,
                'post_type' => 'car',
                'post_status' => 'publish'
            ]);

            if(is_wp_error($inserted_car)) {
                continue;
            }
            $fillable = [
                ...
                'field_61f2d2e5131b1' => $car['Pictures'][0],
                ...
            ];

            foreach($fillable as $key => $name) {
                update_field($key, $name, $inserted_car);
            };
        } else {
            $existing_car_id = $existing_car->ID;
            $existing_car_timestamp = get_field('ModifiedDate', $existing_car_id);

            if($car['ModifiedDate'] >= $existing_car_timestamp){
                $fillable = [
                ...
                'field_61f2d2e5131b1' => $car['Pictures'][0],
                ...
            ];

            foreach($fillable as $key => $name) {
                update_field($key, $name, $existing_car_id);
            };
            }
        }
    }
    print_r('You can now close this page. Your cars are updated');
}
add_shortcode('get_cars_from_api', 'get_cars_from_api');