Почему не работает фильтр?

<form action="users.tpl.php" method="post">
    <label class="col-md-4 control-label" for="newRole">Найти студента</label>
    <input type="text" name="valueToSearch" placeholder="Поиск студентов..." ng-model="searchText" class="form-control "/>
    <input type="submit" name="search"  class="btn btn-default" value="Фильтр"/>
</form>

<?php 
   if (isset($_POST['search'])){
       $valueToSearch = $_POST['valueToSearch'];
       $query = "SELECT * FROM `users` WHERE concat(`fullName`, `group_name`) like '%" . $valueToSearch . "%'";
       $search_result = filterTable($query);
       
   } else {
       $query = "select * from `users` where role_id=2 order by fullName";
       $search_result = filterTable($query);
   }
   
   function filterTable($query){
       $conn = mysqli_connect('XXX', 'XXX', 'XXX', 'XXX');
       $filter_Result = mysqli_query($conn, $query);
       return $filter_Result;
}
?>

<table  id="myTable" class="table table-bordered table-hover table-striped">
<thead>
    <tr>
        <th>ФИО</th>
        <th>Группа</th>
        <th>Логин</th>
        <th>Email</th>
    </tr>
</thead>
<tbody>
<?php
    while ($row = mysqli_fetch_array($search_result)) { ?>
        <tr data-ng-click="showEditForm(); getUserData(<?php echo $row['id'];?>);" >
            <td><?php echo $row['fullName']; ?></td>
            <td><?php echo $row['group_name']; ?></td>
            <td><?php echo $row['login']; ?></td>
            <td><?php echo $row['email']; ?></td>
            
        </tr>
    <?php } ?>
</tbody>
</table>