passaggio valore tra select

[seokey]

Salve a tutti,

nel seguente codice inserisco articoli nel DB. Seleziono categoria e poi dovrei poter associare la sottocategoria inserita. Devo effettuare un refresh... utilizzare javascript oppure c'è una soluzione con php? Grazie mille per l'attenzione.

<form action="articoli.php" method="post" enctype="multipart/form-data" name="form1">
  <label>
  <input name="posted" type="hidden" id="posted" value="posted" />
  

  </label>
  


    <label></label>
  </p>
  <table width="800" border="0">
    <tr>
      <td bgcolor="#000033"><span class="Stile25">categorie</span></td>
      <td bgcolor="#000033"><span class="Stile25">
        <label>subcategoria</label>
      </span></td>
      </tr>
    <tr>
      <td bgcolor="#999999"><span class="Stile29">
        <label>
        <?php 
  include ("config.inc.php"); 
  include ("connect.php");
    
  $query ="SELECT idcat, categoria FROM democat ORDER BY idcat";
  $result = mysql_query($query,$db);
     echo  "<select name=\"idcat\">";
  while ($row = mysql_fetch_array($result)) {
  echo "<option value=\"".$row['idcat']."\">".$row['categoria']."</option>";}
  echo"</select>"; 
  ?>
        </label>
      </span></td>
      <td bgcolor="#999999"><?php 
  //include ("config.inc.php"); 
  //include ("connect.php");
    
  $query ="SELECT * FROM democat AS c, demosubcat AS s, WHERE idcat.c ='idcat.s'";
  $result = mysql_query($query,$db);
     echo  "<select name=\"subcategoria\">";
  while ($row = mysql_fetch_array($result)) {
  echo "<option value=\"".$row['subcategoria']."\">".$row['subcategoria']."</option>";}
  echo"</select>"; ?></td>
    </tr>
    <tr>
      <td bgcolor="#000033"><span class="Stile25">descrizione promo</span></td>
      <td bgcolor="#000033"><span class="Stile25">
        <label>articolo</label>
      </span></td>
    </tr>
    <tr>
      <td bgcolor="#999999"><span class="Stile20"><?php echo '<textarea style="color: red; background-color: yellow" name="descrizione" cols="40" rows="5" id="descrizione"></textarea>'; ?></span></td>
      <td bgcolor="#999999"><span class="Stile29"><?php echo '<input type="text" name="articolo" id="articolo">'; ?></span></td>
    </tr>
    <tr>
      <td bgcolor="#000033"><span class="Stile25">prezzo</span></td>
      <td bgcolor="#000033"><span class="Stile25">descrizione dettaglio</span></td>
    </tr>
    <tr>
      <td bgcolor="#999999"><span class="Stile20"><?php echo '<input type="text" STYLE="color: #FFFFFF; font-family: Verdana; font-weight: bold; font-size: 12px; background-color: #72A4D2;" name="prezzo" id="prezzo">'; ?></span></td>
      <td bgcolor="#999999"><span class="Stile20">
        <label></label>
        <?php echo '<textarea style="color: red; background-color: yellow" name="dettaglio" cols="40" rows="5" id="dettaglio"></textarea>'; ?></span></td>
    </tr>
    <tr>
      <td bgcolor="#000033"><span class="Stile25">immagine principale</span></td>
      <td bgcolor="#000033"><span class="Stile25">sconto</span></td>
    </tr>
    <tr>
      <td bgcolor="#999999"><span class="Stile18"><?php echo '<input type="file" name="userfile" id="userfile">'; ?></span></td>
      <td bgcolor="#999999"><span class="Stile20">
        <label><?php echo '<input type="text" size="20" name="sconto" id="sconto">'; ?></label>
%</span></td>
    </tr>
    <tr>
      <td bgcolor="#000033"><span class="Stile25">immagine 3</span></td>
      <td bgcolor="#000033"><span class="Stile18"><span class="Stile25">immagine 2</span></span></td>
    </tr>
    <tr>
      <td bgcolor="#999999"><span class="Stile18">
        <label><?php echo '<input type="file" name="userfile3" id="userfile3">'; ?> </label>
</span></td>
      <td bgcolor="#999999"><span class="Stile18"><?php echo '<input type="file" name="userfile2" id="userfile2">'; ?></span></td>
    </tr>
  </table>
  <table width="800" border="0">
    <tr>
      <td width="22" bgcolor="#000033"><span class="Stile30"><?php echo '<input type="checkbox" name="promozioni" id="promozioni">'; ?></span></td>
      <td width="233" bgcolor="#000033"><span class="Stile25">
        <label>promozioni</label>
      </span></td>
      <td width="21" bgcolor="#000033"><span class="Stile25"><?php echo '<input type="checkbox" name="novita" id="novita">'; ?></span></td>
      <td width="82" bgcolor="#000033"><span class="Stile25">novit&agrave;</span></td>
      <td width="21" bgcolor="#000033"><span class="Stile25"><?php echo '<input type="checkbox" name="esclusivo" id="esclusivo">'; ?></span></td>
      <td width="214" bgcolor="#000033"><span class="Stile25">esclusivo</span></td>
      <td width="177" bgcolor="#000033"><?php echo '<input type="submit" name="invia" id="invia" value="AGGIUNGI" STYLE="font-family:sans-serif; font-size: 10px;
font-style:bold; background:#006699 none; color: #FFFFFF; width:8em">'; ?></td>
    </tr>
  </table>
  
  

</p>
</form>