<script>
     window.onload = function() {
      function and do not restore data
         if (sessionStorage.getItem('user') == " ") {
             return;
         }
                if (sessionStorage.getItem('user') == " ") {
             return;
         }
         var user = sessionStorage.getItem('user');
         if (user !== null) $('#user').val(user);
           window.onbeforeunload = function() {
           sessionStorage.setItem("user", $('#user').val());
     }
 </script>

<select name="user" id="user" class="form-control">
    <option value="">Все</option>
        <?php
          while($test = mysqli_fetch_array($result)) {
           $name = $test["userName"];
           echo '<option value="'.$name.'">'. $name .'</option>';
                    }
                        ?>
                    </select>