Removes users (subscribers) on a WordPress site who haven't yet enrolled in a LearnDash course

remove-learndash-subscribers-who-are-not-enrolled.php

add_action( 'wp_loaded', 'bhww_remove_subscriber_users_not_enrolled' );
/**
 * Remove users who are only subscribers and who are not yet enrolled in the course.
 * Only runs when a WordPress admin page loads.
 */
function bhww_remove_subscriber_users_not_enrolled() {

	// If this is not the WP admin, return early
	if ( ! is_admin() )
		return;

	$args = array(
		'role__not_in' => array( 'administrator', 'editor', 'author', 'group_leader' ),
		'orderby'      => 'ID',
		'order'        => 'desc',
		'number'       => 100, // change this number as needed
	);

	// Array of WP_User objects
	$subscribers = get_users( $args );

	$current_time = time();

	foreach ( $subscribers as $user ) {

		$user_id   = $user->ID;
		$user_name = $user->user_login;
		$course_id = 580; // LearnDash course ID - change as needed

		$enrolled_in   = learndash_user_get_enrolled_courses( $user_id );
		$quiz_progress = get_user_meta( $user_id, '_sfwd-quizzes', true );

		$get_mysql_time = current_time( 'mysql' );

		$registered_date_time = $user->user_registered;
		$timestamp            = strtotime( $registered_date_time );

		// Registered for at least 15 minutes?
		$timestamp_plus_fifteen_minutes = $timestamp + 900;

		if ( empty( $enrolled_in ) && empty( $quiz_progress ) ) {

			// Registered more than fifteen minutes ago and haven't paid yet? Delete the user.
			if ( $timestamp_plus_fifteen_minutes < $current_time ) {

				// https://developer.wordpress.org/reference/functions/wp_delete_user/
				require_once( ABSPATH . 'wp-admin/includes/user.php' ); // Need this for wp_delete_user()
				wp_delete_user( $user_id );

			}

		}

	}

}