ragazzi ho una form realizzata con delle tabelle, quello che dovrebbe fare è (per gli esperti) molto semplice, l'utente inserisce l'importo, inserisce l'iva, e il programma dovrebbe restituire nella colonna Totale l'importo ivato. Sto impazzando perchè non so come implementare il calcolo.

Mi dareste una mano ?

codice:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Commessa Officina</title>
<style type="text/css">
#container {
	width: 700px;
}


#salva {
	margin-left: 50px;
	margin-bottom: 10px;
	float: right;
}
</style>
</head>


<body>
<?php
$imp1 = $importo1;
$iva = 22;
$totale = $imp1*$iva;
?>


<div id="container"> <!-- apro il div container -->
<FORM method="POST" action="miosito">
<fieldset>
  <legend>Anagrafica Cliente</legend>
  <div id="anagrafica">
    <table width="615" border="1" cellpadding="3" cellspacing="1" bordercolor="#FFCC00" style="background-color:#FFFFCC">
      <tr>
        <td width="99">Id</td>
        <td width="495"><input name="id" disabled="disabled" id="id" value="0" size="10" readonly="readonly"></td>
        </tr>
      <tr>
        <td>Cliente</td>
        <td><input name="cliente" id="cliente"></td>
        </tr>
      <tr>
        <td>Indirizzo</td>
        <td><input name="indirizzo" id="indirizzo"></td>
        </tr>
      <tr>
        <td>Partita Iva</td>
        <td><input name="piva" id="piva" maxlength="12"></td>
        </tr>
      <tr>
        <td>Telefono</td>
        <td><input name="tel" id="tel"></td>
        </tr>
    </table>
</fieldset>


<fieldset>
  <legend>Anagrafica Vettura</legend>
    <table width="615" border="1" cellpadding="3" cellspacing="1" bordercolor="#FFCC00" style="background-color:#FFFFCC">
      <td width="99">Veicolo</td>
        <td width="145"><input name="veicolo" id="veicolo"></td>
        </tr>
      <tr>
        <td>Targa</td>
        <td><input name="targa" id="targa"></td>
        </tr>
      <tr>
        <td>Telaio</td>
        <td><input name="telaio" id="telaio"></td>
        </tr>
      <tr>
        <td>Km</td>
        <td><input name="km" id="km"></td>
        <td width="54">Nome tecnico</td>
        <td width="278"><input name="n_tecnico" id="n_tecnico"></td>
        </tr>
    </table>
</fieldset>
<fieldset>
<legend>Interventi</legend>
<table width="575" border="1" cellpadding="3" cellspacing="1" bordercolor="#FFCC00" style="background-color:#FFFFCC">
        <td width="144">Intervento</td>
      	<td width="144">Importo</td>
        <td width="144">Iva</td>
        <td width="142">Totale</td>
        </tr>
      <tr>
        </tr>
      <tr>
        <td><input name="int_1" id="int_1"></td>
        <td><input name="imp_1" id="imp_1" value= <?php "$importo1"; ?>></td>
        <td><input name="iva_1" id="iva_1"></td>
        <td><input name="tot_1" id="tot_1" value="<?php echo $totale; ?>" readonly="readonly"></td>
        </tr>
      <tr>
        <td><input name="int_2" id="int_2"></td>
        <td><input name="imp_2" id="imp_2"></td>
        <td><input name="iva_2" id="iva_2"></td>
        <td><input name="tot_2" id="tot_2"></td>
        </tr>
        
        <tr>
        <td><input name="int_3" id="int_3"></td>
        <td><input name="imp_3" id="imp_3"></td>
        <td><input name="iva_3" id="iva_3"></td>
        <td><input name="tot_3" id="tot_3"></td>
        </tr>
        
        <tr>
        <td><input name="int_4" id="int_4"></td>
        <td><input name="imp_4" id="imp_4"></td>
        <td><input name="iva_4" id="iva_4"></td>
        <td><input name="tot_4" id="tot_4"></td>
        </tr>
        
        <tr>
        <td><input name="int_5" id="int_5"></td>
        <td><input name="imp_5" id="imp_5"></td>
        <td><input name="iva_5" id="iva_5"></td>
        <td><input name="tot_5" id="tot_5"></td>
        </tr> 
        
        <tr>
        <td><input name="int_6" id="int_6"></td>
        <td><input name="imp_6" id="imp_6"></td>
        <td><input name="iva_6" id="iva_6"></td>
        <td><input name="tot_6" id="tot_6"></td>
        </tr>
        
        <tr>
        <td><input name="int_7" id="int_7"></td>
        <td><input name="imp_7" id="imp_7"></td>
        <td><input name="iva_7" id="iva_7"></td>
        <td><input name="tot_7" id="tot_7"></td>
        </tr>    
        
        <tr>
        <td><input name="int_8" id="int_8"></td>
        <td><input name="imp_8" id="imp_8"></td>
        <td><input name="iva_8" id="iva_8"></td>
        <td><input name="tot_8" id="tot_8"></td>
        </tr>
        
        <tr>
        <td><input name="int_9" id="int_9"></td>
        <td><input name="imp_9" id="imp_9"></td>
        <td><input name="iva_9" id="iva_9"></td>
        <td><input name="tot_9" id="tot_9"></td>
        </tr> 
        
        <tr>
        <td><input name="int_10" id="int_10"></td>
        <td><input name="imp_10" id="imp_10"></td>
        <td><input name="iva_10" id="iva_10"></td>
        <td><input name="tot_10" id="tot_10"></td>
        </tr>
                 
        </table>
</fieldset>
<div id="salva">
<input type="submit" value="Salva" />
</div>
</FORM>
</div> <!-- chiudo il div container -->
</body>
</html>
Grazie