CoursePress: Enroll new registered user to all available courses. Be careful it can break your site if you have a lot of available courses.

enroll-new-to-all-courses.php

<?php
/**
 * Plugin Name: Enroll new user!
 * Plugin URI: https://premium.wpmudev.org/
 * Description: Enroll new registered user to all available courses. Be careful it can break your site if you have a lot of available courses.
 * Version: 1.0
 * Author: Marcin Pietrzak (Incsub)
 * Author URI: https://premium.wpmudev.org/profile/marcin10
 * License: GPL2+
 */

add_action('user_register', 'coursepress_custom_enroll_for_all');

function coursepress_custom_enroll_for_all( $student_id ) {
    /**
     * get post id for anny published courses
     */
    $args = array(
        'post_type' => CoursePress_Data_Course::get_post_type_name(),
        'nopaging' => true,
        'status' => array( 'publish' ),
        'fields' => 'ids',
    );
    $the_query = new WP_Query( $args );
    if ( $the_query->have_posts() ) {
        while ( $the_query->have_posts() ) {
            $the_query->the_post();
            $course_id = get_the_ID();
            /**
             * avoid to add to full courses
             */
            if ( CoursePress_Data_Course::is_full( $course_id ) ) {
                continue;
            }
            /**
             * enroll student to course
             */
            CoursePress_Data_Course::enroll_student( $student_id, $course_id );
        }
    }
}