Try someting in this order (seems better to me)
<form>
<table>
<tr>
<td>...
</td>
<td>...
</td>
<td>
<?php echo('<input type="submit" value="Concluido" name="submit.'['.$row['id'].']'. '" class="enviar" />'?>
</td>
</tr>
</table>
</form>
//Check button
<?php
if (isset($_POST['submit'])) {
reset($_POST['submit']);
foreach ($_POST['submit'] as $name => $value) {
//do some update on ... $name);
}
}
?>