In development mode.
use Invoice\InvoiceApi;
use Invoice\Invoice;
use Invoice\InvoiceItem;
$invoiceApi = new InvoiceApi('*APIKEY*');
$invoiceItem = new InvoiceItem();
$invoiceItem
->setQuantity(10)
->setPrice(2.4)
->setVat(20);
$invoice = new Invoice();
$invoice
->setName('Invoice 12323')
->setDescription('invoice description...')
->addItem($invoiceItem);
// there are other method to set invoice properties...
$result = $invoiceApi->createInvoice($invoice);
if ($result->isOK()) {
echo "Download pdf: " . $result->getDownloadUrl() . "\n";
echo "Online HTML version:" . $result->getHtmlUrl() . "\n";
} else {
echo "Error: " . $result->getErrorMessage() . "\n";
}