Ya que no tienen soporte para este tipo de consultas por eso os pregunto a vosotros. A continuación os muestro del formulario y el script que me mandaron:
Codigo formulario html
Código PHP:
<html>
<head><title>Empres</title></head>
<body>
<form name="form1" method="post" action="pago.php">
<table width="55%">
<tr>
<td colspan="2"> <h2>Empresa</h2>
</td>
</tr>
<tr>
<td>Titular: </td>
<td><input type="text" name="titular" value="titular"></td>
</tr>
<tr>
<td>Importe: </td>
<td><input type="text" name="importe"></td>
</tr>
<tr><td><input type="submit" value="Pagar"></td></tr>
</table>
</form>
</body>
</html>
Código PHP:
<?PHP
<?PHP
// If form is submitted with all required data then show the form
// else show error page
//$importe=230;
empty($Formulario) ?
ShowForm($importe,$titular):
ShowError();
exit;
?>
<?PHP
.......
.......//Algoritmos de encriptacion
function ShowError () {
echo "<html><head><title>Results</title></head><body>
<table width=100% height=50%><tr><td>
<p><h2><center>Compruebe que todos los datos del formulario son correctos!!</center></h2></p>
</td></tr></table>
</body></html>\n";
} # End of function ShowResults
function ShowForm ($importe,$titular) {
// Posted data
global $HTTP_POST_VARS;
// Now, print the HTML script
$url = 'https://sis.sermepa.es/sis/realizarPago';
echo "<html><head><title>Comercio Simulador</title></head>
<body bgcolor=white>
<form name=form1 action=$url method=post>";
$order = uniqid(1);
$order = '1234' . substr($order, 1,9);
$code = 'codemio';
$currency = '978';
$clave = 'clavemia'; //
$importe = $importe*100;
echo "
<input type=hidden name=Ds_Merchant_Amount value=$importe>
<input type=hidden name=Ds_Merchant_Titular value=$titular>
<input type=HIDDEN name=Ds_Merchant_ConsumerLanguage value=001>
<input type=HIDDEN name=Ds_Merchant_Currency value=$currency>
<input type=HIDDEN name=Ds_Merchant_Order value=$order>
<input type=HIDDEN name=Ds_Merchant_MerchantCode value=$code>
<input type=HIDDEN name=Ds_Merchant_Terminal value=001>
<input type=HIDDEN name=Ds_Merchant_ProductDescription>
<input type=HIDDEN name=Ds_Merchant_MerchantURL>
<input type=HIDDEN name=Ds_Merchant_MerchantName value=Empresa>"; //
// Compute hash to sign form data
// $signature=sha1_hex($importe,$order,$code,$currency,$clave);
$sha = new SHA;
$message = $importe.$order.$code.$currency.$clave;
$digest1 = $sha->hash_string($message);
$signature = strtoupper ($sha->hash_to_string( $digest1 ));
echo "<input type=hidden name=Ds_Merchant_MerchantSignature value='$signature'>
<center><script language=javascript>document.form1.submit();</script></center>
</form>
</body></html>";
} # End of function ShowForm
?>
... 
