<table cellpadding="0" cellspacing="0">
<thead>
<tr>
<td style="width:20px;">[img]images/ricerca.gif[/img]</td>
<td>

Ricerca semplice</p></td>
</tr>
</thead>
</table>
<form method="post" action="../script/motore.php" style="margin:0px;padding:0px;">
<table cellpadding="0" cellspacing="0">
<tbody>
<tr>
<td>

Parola chiave</p></td>
<td>

<input type="text" name="key" class="input" style="width:160px;" /></p></td>
</tr>
<tr>
<td>

Tipo</p></td>
<td>

<select name="vendo_compro" style="width:160px;"><option value="all">Tutti gli annunci</option><option value="v" >Vendo / Offro</option><option value="c" >Compro / Cerco</option>
</select></p></td>
</tr>
<?php

mysql_connect("localhost", "root", "");
mysql_select_db("mercato");

$listCAT='';
$sql = 'SELECT * FROM categorie WHERE id=root ORDER BY nome ASC';
$query = @mysql_query ($sql);
$num = @mysql_num_rows ($query);
while ($row = @mysql_fetch_array ($query)){
$listCAT.='<option value="'.$row['id'].'" readonly>'.ucfirst($row['nome']).'</option>';
$sql = 'SELECT * FROM categorie WHERE id!=root AND root='.$row['id'];
$query2 = @mysql_query ($sql);
while ($row2 = @mysql_fetch_array ($query2)){
$listCAT.='<option value="'.$row2['id'].'" >'.ucfirst($row2['nome']).'</option>';
}
}
?>
<tr>
<td>

Categoria</p></td>
<td>

<select name="categoria" style="width:160px;"><option value="all">Tutte le categorie</option><?php echo $listCAT ?></select></p></td>
</tr>
<tr>
<td>

Tipo</p></td>
<td>

<select name="nuovo_usato" style="width:160px;"><option value="all">Tutti i tipi</option><option value="n" >Nuovo</option><option value="u" >Usato</option></select></p></td>
</tr>
<tr>
<td>

</p></td>
<td><p align="left"><input type="submit" class="submit" name="easy" value=" cerca " /></p></td>
</tr>
</tbody>
</table>
</form>

Struttura tabella ANNUNCI (quella dove faccio la query):
id, titolo, prezzo, categoria (assume dei numeri da un'altra tabella), vendo_compro (assume valori v/c), nuovo_usato (assume valori n/u), testo.