Add Custom Email Notifications for WordPress User Registrations

Code

<?php
// Hook into user registration to send a custom email
add_action('user_register', 'wp_dudecom_send_custom_welcome_email', 10, 1);

/**
 * Send a custom welcome email to new users upon registration.
 *
 * @param int $user_id The ID of the newly registered user.
 */
function wp_dudecom_send_custom_welcome_email($user_id) {
    // Get user data
    $user_info = get_userdata($user_id);
    $user_email = $user_info->user_email;
    $user_name = $user_info->user_login;

    // Set email subject and message
    $subject = 'Welcome to Our Website!';
    $message = sprintf('Hello %s, welcome to our website! We are glad to have you.', $user_name);

    // Set email headers
    $headers = array('Content-Type: text/html; charset=UTF-8');

    // Send the email
    wp_mail($user_email, $subject, $message, $headers);
}

// Hook into the registration form to add custom fields
add_action('register_form', 'wp_dudecom_add_custom_registration_fields');

/**
 * Add custom fields to the WordPress registration form.
 */
function wp_dudecom_add_custom_registration_fields() {
    ?>
    <p>
        <label for="phone"><?php _e('Phone Number', 'wp-dudecom'); ?><br/>
            <input type="text" name="phone" id="phone" class="input" value="<?php echo esc_attr(wp_unslash($_POST['phone'] ?? '')); ?>" size="25" /></label>
    </p>
    <?php
}

// Hook into user registration to save custom fields
add_action('user_register', 'wp_dudecom_save_custom_registration_fields');

/**
 * Save custom registration fields to user meta.
 *
 * @param int $user_id The ID of the newly registered user.
 */
function wp_dudecom_save_custom_registration_fields($user_id) {
    if (isset($_POST['phone'])) {
        update_user_meta($user_id, 'phone', sanitize_text_field($_POST['phone']));
    }
}

// Hook to modify the admin email notification
add_filter('wp_new_user_notification_email', 'wp_dudecom_custom_admin_notification_email', 10, 3);

/**
 * Customize the admin email notification for new user registration.
 *
 * @param array $wp_new_user_notification_email The email data.
 * @param WP_User $user The user object.
 * @param string $blogname The name of the blog.
 * @return array Modified email data.
 */
function wp_dudecom_custom_admin_notification_email($wp_new_user_notification_email, $user, $blogname) {
    $wp_new_user_notification_email['subject'] = sprintf('[%s] New User Registration: %s', $blogname, $user->user_login);
    $wp_new_user_notification_email['message'] = sprintf('A new user has registered on your site %s. Username: %s', $blogname, $user->user_login);

    return $wp_new_user_notification_email;
}
?>