function dozent_enrol_course( $course = null, $user = null, $order_id = null, $expired_at = '' ) {

		$course = dozent_get_course( $course );
		$user   = dozent_user_data( $user );

		do_action( 'dozent_enrol_before', $course, $user );

		$enrol = $user->enrol_course( $course, $order_id, $expired_at );

		do_action( 'dozent_enrol_after', $enrol );

		/**
		 * Filter enrolment status which return by the dozent_enrol_course(); function
		 *
		 * @since DozentLMS 1.0.0
		 *
		 * @param  bool|object  $enrol  enrolment data on success, false on fail
		 * @param  object  $course  course object
		 * @param  object  $user  user data as object
		 *
		 */

		return apply_filters( 'dozent_enrol_course', $enrol, $course, $user );
	}