Make a php routine check every 30 seconds

I have this code running on the header of my site :

<?php if(($Variable1 > 0) && (isset($_SESSION["role"]) && ($_SESSION["role"]==12 || $_SESSION["role"]==13))){ ?>
            <button type="button" class="btn btn-danger btn-block btn-block"><i class="fa fa-exclamation-triangle">
            </i> Number Left: <?php echo $NumberLeft; ?></button>
            <?php } ?>

i want this code to run every 30 seconds

I cant make a page regresh every 30 seconds because i’m losing the data that is not saved till then in that page. So i need only the check of the specific banner .
I tried refreshing the header but its refreshing the whole page