Use YouTube Thumbnail as Featured Image

// Hook into the save_post action to set the YouTube thumbnail as the featured image

function set_youtube_thumbnail_as_featured_image($post_id) {

    // Check if the post type is 'video' to avoid running on other post types

    if (get_post_type($post_id) !== 'video') {

        return;

    }

    // Avoid infinite loop when updating the post

    if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) {

        return;

    }

    // Get the YouTube video URL (from the custom field 'video_url')

    $youtube_url = get_post_meta($post_id, 'video_url', true);

    if (!$youtube_url) {

        return;

    }

    // Extract the video ID from the YouTube URL

    preg_match('/(?:youtube\.com\/(?:[^\/\n\s]+\/\S+\/|(?:v|e(?:mbed)?)\/|\S*?[?&]v=)|youtu\.be\/)([a-zA-Z0-9_-]{11})/', $youtube_url, $matches);

    if (isset($matches[1])) {

        $video_id = $matches[1];

        // Check availability of thumbnails

        $thumbnail_urls = [

            "https://img.youtube.com/vi/$video_id/maxresdefault.jpg", // Max-res thumbnail

            "https://img.youtube.com/vi/$video_id/sddefault.jpg",    // Standard definition

            "https://img.youtube.com/vi/$video_id/hqdefault.jpg",    // High quality

            "https://img.youtube.com/vi/$video_id/mqdefault.jpg"     // Medium/normal quality

        ];

        $thumbnail_url = null;

        foreach ($thumbnail_urls as $url) {

            // Use cURL to check if the thumbnail exists

            $ch = curl_init($url);

            curl_setopt($ch, CURLOPT_NOBODY, true);

            curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

            curl_setopt($ch, CURLOPT_TIMEOUT, 5);

            curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);

            curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);

            curl_exec($ch);

            $http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);

            curl_close($ch);

            // If the thumbnail is found (HTTP 200), use this URL

            if ($http_code === 200) {

                $thumbnail_url = $url;

                break;

            }

        }

        if ($thumbnail_url) {

            // Download the image

            $image_data = file_get_contents($thumbnail_url);

            if ($image_data) {

                // Get the upload directory path

                $upload_dir = wp_upload_dir();

                // Define the path for the new image

                $image_path = $upload_dir['path'] . '/' . $video_id . '.jpg';

                // Save the image to the server

                file_put_contents($image_path, $image_data);

                // Check the file type

                $filetype = wp_check_filetype($image_path, null);

                // Prepare attachment data

                $attachment = array(

                    'guid' => $upload_dir['url'] . '/' . basename($image_path),

                    'post_mime_type' => $filetype['type'],

                    'post_title' => sanitize_file_name(basename($image_path)),

                    'post_content' => '',

                    'post_status' => 'inherit',

                );

                // Insert the attachment into the media library

                $attach_id = wp_insert_attachment($attachment, $image_path, $post_id);

                // Generate metadata for the attachment

                require_once(ABSPATH . 'wp-admin/includes/image.php');

                $attach_data = wp_generate_attachment_metadata($attach_id, $image_path);

                wp_update_attachment_metadata($attach_id, $attach_data);

                // Set the post thumbnail

                set_post_thumbnail($post_id, $attach_id);

            }

        }

    }

}

// Add the function to the 'save_post' hook

add_action('save_post', 'set_youtube_thumbnail_as_featured_image');