public static function chargeInvoiceArbitraryAmount($contactId, $invoiceId, $cardId, $amount, $merchantAccountId, $invoiceNotes = 'API Arbitrary Payment')
 {
     //Create a new order (InvoiceService.blankOrder...
     $dummyInvoiceId = Infusionsoft_InvoiceService::createBlankOrder($contactId, $invoiceNotes . " Invoice: " . $amount, date('Ymd\\TH:i:s'));
     try {
         //Add an order item that is the correct amount you want to charge...
         Infusionsoft_InvoiceService::addOrderItem($dummyInvoiceId, 0, 3, $amount, 1, $invoiceNotes . " order", "");
         //Set orders custom field "_ChargeStatus" to "Pending"
         $invoice = new Infusionsoft_Invoice($dummyInvoiceId);
         $dummyOrder = new Infusionsoft_Job($invoice->JobId);
         $dummyOrder->OrderStatus = "Pending";
         $dummyOrder->save();
         //Try to charge the invoice
         $result = Infusionsoft_InvoiceService::chargeInvoice($dummyInvoiceId, $invoiceNotes . " payment", $cardId, $merchantAccountId, false);
     } catch (Exception $e) {
         Infusionsoft_InvoiceService::deleteInvoice($dummyInvoiceId);
         throw new Exception("Failed to charge partial payment. Infusionsoft says: " . $e->getMessage());
     }
     //Update order status "_ChargeStatus" to "Failed", or "Succeeded"
     if ($result['Successful']) {
         //add a credit to the order
         Infusionsoft_InvoiceService::addManualPayment($invoiceId, $amount, date('Ymd\\TH:i:s'), "Credit Card", $invoiceNotes . " partial payment", false);
         $dummyOrder->OrderStatus = "Successful";
         $dummyOrder->save();
     } else {
         //erase the invoice
         Infusionsoft_InvoiceService::deleteInvoice($dummyInvoiceId);
     }
     return $result;
     //Update order status to "Applied"
 }
<form>
            invoiceId: <input type="text" name="invoiceId" value="<?php 
if (isset($_REQUEST['invoiceId'])) {
    echo htmlspecialchars($_REQUEST['invoiceId']);
}
?>
"><br/>
    <input type="submit">
<input type="hidden" name="go">
</form>
<?php 
include '../infusionsoft.php';
include 'testUtils.php';
if (isset($_REQUEST['go'])) {
    $out = Infusionsoft_InvoiceService::deleteInvoice($_REQUEST['invoiceId']);
    var_dump($out);
}