Select dinamica, php o javascript?

[MacApp]

Prova così:

<? if ($_post['mm'] != '') { $mm = $_post['mm'];} ?>

<? echo "<form name='inputform' method='post' action='".$PHP_SELF."'";
echo "<select class='textbox' name='mm' onchange='submit();'>"; 
for ($i=1; $i<=12; $i++) {
if ($i == $mm) {echo "<option value='".$i."' selected>".$i."</option>";}
else {echo "<option value='".$i."'>".$i."</option>"; }
}
echo "</select>
</form>"; ?>