echo '<table>';
echo '<thead>';
echo '<tr>';
echo '<th>MON$ATTACHMENT_ID</th>';
echo '<th>MON$USER</th>';
echo '<th>MON$TIMESTAMP</th>';
echo '<th>MON$REMOTE_PROCESS</th>';
echo '</tr>';
echo '</thead>';
$host = 'localhost:D:\FDBase\TEST.FDB'; 
$connection = ibase_connect($host, 'SYSDBA', 'masterkey', 'UTF8') or die(ibase_errmsg()) ;
$query='select MON$ATTACHMENT_ID , MON$USER, MON$TIMESTAMP, MON$REMOTE_PROCESS from MON$ATTACHMENTS';
$result=ibase_query($connection, $query) or die(ibase_errmsg());
echo '<tbody>';
while($row = ibase_fetch_assoc($result)) 
{
  echo '<tr>';
  echo '<td>' . $row['MON$ATTACHMENT_ID'] . '</td>';
  echo '<td>' . $row['MON$USER'] . '</td>';
  echo '<td>' . $row['MON$TIMESTAMP'] . '</td>';
  echo '<td>' . $row['MON$REMOTE_PROCESS'] . '</td>' . 
  echo '</tr>';
}
echo '</tbody>';
echo '</table>';
ibase_free_result($result); // про это ты забыл
ibase_close($connection);