Something

<?php
include("connect.php");
$query="select * from subcat where cat_id=".$_GET['categorie'];
$result=mysql_query($query);
$response = 'subcategorie<br>';
$response .= "<select id=subcat name=subcat onchange=\"ajaxFunction_actiuni('subcat_actiuni')\"\">";
 $response .= '<option value="">-selectati subcategoria-</option>';
 for($k=0;$k<@mysql_numrows($result);$k++)
 $response .= '<option value="'.mysql_result($result,$k,"id").'">'.mysql_result($result,$k,"nume").'</option>';
$response .= '</select>';
echo $response;
?>