Cant update invoice using API?

[Seiya]

Hi, Im trying my best to update an invoice using the API. All items within the invoice should be discounted but I can't seem to get it to work. Can anyone spare a minute to check the code, I am far from a pro..

 

<?php

$discount=0.50;
$discountpercent=$discount*100;

/* retrieve invoice using WHMCS API */
$url = "http://xxxxx/whmcs/includes/api.php";
$username = "xxxxx";
$password = "xxxxx";
$postfields["username"] = $username;
$postfields["password"] = md5($password);
$postfields["action"] = "getinvoice";
$postfields["invoiceid"] = "1234";

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_TIMEOUT, 100);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $postfields);
$data = curl_exec($ch);
curl_close($ch);

$xml = new SimpleXMLElement($data);
echo '<pre>'.print_r($xml).'</pre>';

$array_amount = array();
$array_description = array();

foreach ($xml->items->item as $item) {
   $itemid=$item->id;
   $itemamount=$item->amount;
   $discountamount=round(($itemamount*(1-$discount)),2);
   $newdescription="$item->description with $discountpercent% discount";
   $array_amount["$itemid"]=$discountamount;
   $array_description["$itemid"]=$newdescription;
}        

/* Update invoice using WHMCS API */
$postfields["action"] = "updateinvoice";
$postfields["invoiceid"] = "1234";
$postfields["itemdescription"] = $array_description;
$postfields["itemamount"] = $array_amount;

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_TIMEOUT, 100);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $postfields);
$data = curl_exec($ch);
curl_close($ch);

$data = explode(";",$data);
foreach ($data AS $temp) {
 $temp = explode("=",$temp);
 $results[$temp[0]] = $temp[1];
}

if ($results["result"]=="success") {
 echo "<p>Success</p>";
} else {
 # An error occured
 echo "The following error occured: ".$results["message"];
}

?>

[othellotech]

$discountamount=round(($itemamount*(1-$discount)),2);

should be

$discountamount=round(($itemamount-($itemamount*$discount)),2);

[Seiya]

Thanks to Matt, he suggested using a query string rather than trying to curl post the arrays. This worked beautifully!