Database echoën geeft lege velden

<?php    if (isset($_GET['leden'])) {
        echo '<span style="color:green; font-weight: bold">Overzicht van onze leden!</span>';

$con = mysql_connect("localhost","mijngebruiker","mijnpass");
if (!$con)
  {
  die('Could not connect: ' . mysql_error());
  }

mysql_select_db("mijndatabasenaam", $con);

$result = mysql_query("SELECT * FROM gebruikers");

echo "<table border='1'>
<tr>
<th>ID</th>
<th>Voornaam</th>
<th>Achternaam</th>
<th>Geslacht</th>
<th>Telefoon</th>
</tr>";

while($row = mysql_fetch_array($result))
  {
  echo "<tr>";
  echo "<td>" . $row['id'] . "</td>";
  echo "<td>" . $row['voornaam'] . "</td>";
  echo "<td>" . $row['achternaam'] . "</td>";
  echo "<td>" . $row['geslacht'] . "</td>";
  echo "<td>" . $row['telnr'] . "</td>";
  echo "</tr>";
  }
echo "</table>";

mysql_close($con);
        exit();

    }
?>