MPower PHP Checkout Invoice setup

building_checkout_invoice.php

<?php
/* Adding items to your invoice is very basic, the parameters expected are 
name_of_item, quantity, unit_price, total_price and optional item
description. */
$invoice->addItem("13' Apple Retina 500 HDD",1,10.99,10.99);
$invoice->addItem("Case Logic laptop Bag",2,100.50,201,"Optional description");
$invoice->addItem("Philips electric shaver",2,50.50,101.00);

/* You can optionally set a general invoice description text which can 
be used in cases where your invoice does not need an items list or in cases
where you need to include some extra descriptive information to your invoice */
$invoice->setDescription("Optional Invoice description here");