Send update notification to the users who previously downloaded the package

send-update-notifications.php

<?php
function wpdm_send_update_notification($ID, $post, $update){
    global $wpdb;
    if (get_post_type() != 'wpdmpro' || wp_is_post_revision( $ID ) || $post->post_status !== 'publish') return;
    
    $users = $wpdb->get_results("select uid from {$wpdb->prefix}ahm_download_stats where pid = '{$ID}' and uid != 0");
    $emails = [];
    foreach ($users as $user){
        if((int)$user->uid > 0)
        $emails[] = get_user_by('ID', $user->uid)->user_email;
    }
    $link = get_permalink($ID);
    $title = get_the_title($ID);
    $params = [
        'to'        => "noreply@yourdomain.com",
        'from'      => "admin@yourdomainn.com",
        'bcc'       => implode(",", $emails),
        'subject'   => "Updated: ".$title,
        'message'   => "Hello,<br/>There is an update available for the following item:<br/><a href='{$link}'>{$title}</a>"
    ];
    \WPDM\Email::send("default", $params);
}
add_action('save_post', 'wpdm_send_update_notification', 10, 3);