source: inc/alerts-msg.php

<?php
/**
 * If the "msg" parameter is in the page URL, display the corresponding message.
 */
?>
<?php if ((isset($_GET['msg'])) && (! empty($_GET['msg']))) { ?>
        <div class="alert alert-info" role="alert">
                <?php
                switch ($_GET['msg']) {
                        case 'logged_in':
                                echo 'You have successfully logged in.'; break;
                        case 'review_added':
                                echo 'Your review has been added.'; break;
                        default:
                                echo 'An unknown error has occurred.';
                }
                ?>
        </div>
<?php } ?>