if ( ! in_array( $request['status'], array( 'add', 'remove', 'delete' ), true ) ) {
			return new WP_Error( 400, __( 'Invalid status', 'lifterlms' ) );
		}

		$student_id = intval( $request['student_id'] );
		$post_id    = intval( $request['post_id'] );

		switch ( $request['status'] ) {
			case 'add':
				$res = llms_enroll_student( $student_id, $post_id, 'admin_' . get_current_user_id() );
				break;

			case 'remove':
				$res = llms_unenroll_student( $student_id, $post_id, 'cancelled', 'any' );
				break;

			case 'delete':
				$res = llms_delete_student_enrollment( $student_id, $post_id, 'any' );
				break;
		}

		if ( ! $res ) {
			// Translators: %s = action add|remove|delete.
			return new WP_Error( 400, sprintf( __( 'Action "%1$s" failed. Please try again', 'lifterlms' ), $request['status'] ) );
		}

		return array(
			'success' => true,
		);
	}

	/**
	 * Validate a Coupon via the Checkout Form
	 *
	 * @since 3.0.0
	 * @since 3.39.0 Minor changes to code for readability with no changes to function behavior.
	 * @since 4.21.1 Sanitize user-submitted coupon code before outputting in error messages.
	 *
	 * @param array $request $_POST data.
	 * @return array|WP_Error On success, returns an array containing HTML parts used to update the interface of the checkout screen.
	 *                        On error, returns an error object with details of the encountered error.
	 */
	public static function validate_coupon_code( $request ) {

		$error = new WP_Error();

		$request['code'] = ! empty( $request['code'] ) ? sanitize_text_field( $request['code'] ) : '';

		if ( empty( $request['code'] ) ) {

			$error->add( 'error', __( 'Please enter a coupon code.', 'lifterlms' ) );

		} elseif ( empty( $request['plan_id'] ) ) {

			$error->add( 'error', __( 'Please enter a plan ID.', 'lifterlms' ) );

		} else {

			$cid = llms_find_coupon( $request['code'] );

			if ( ! $cid ) {

				// Translators: %s = coupon code.
				$error->add( 'error', sprintf( __( 'Coupon code "%s" not found.', 'lifterlms' ), $request['code'] ) );

			} else {

				$coupon = new LLMS_Coupon( $cid );
				$valid  = $coupon->is_valid( $request['plan_id'] );

				if ( is_wp_error( $valid ) ) {

					$error = $valid;

				} else {

					llms()->session->set(
						'llms_coupon',
						array(
							'plan_id'   => $request['plan_id'],
							'coupon_id' => $coupon->get( 'id' ),
						)
					);

					$plan = new LLMS_Access_Plan( $request['plan_id'] );

					ob_start();
					llms_get_template(
						'checkout/form-coupon.php',