if(isset($_POST['idpupil'])) {$idpupil = $_POST['idpupil'];}
if(isset($_POST['date'])) {$date = $_POST['date'];}
if(isset($_POST['idteacher'])) {$idteacher = $_POST['idteacher'];}
<?php
$sql_tbl_usrs = "SELECT * FROM users, department, usergroup WHERE users.department = department.id AND users.usergroup = usergroup.id";
$result_tbl_usrs = mysqli_query($connection, $sql_tbl_usrs);
$row_index = 1;
while ($row_tbl_usrs = mysqli_fetch_array($result_tbl_usrs)) {
echo '<tr>
<td>' . $row_index . '</td>
<td>' . $row_tbl_usrs['last_name'] . ' ' . $row_tbl_usrs['first_name'] . ' ' . $row_tbl_usrs['patronymic'] . '</td>
<td>' . $row_tbl_usrs['function'] . '</td>
<td>' . $row_tbl_usrs['department'] . '</td>
<td>' . $row_tbl_usrs['usergroup'] . '</td>
<td>' . $row_tbl_usrs['login'] . '</td>
<td>' . $row_tbl_usrs['date_registration'] . '</td>
</tr>';
$row_index++;
}
?>