aMember (site.php): Add 3 digit unique code to the product price

site.php

<?php

Am_Di::getInstance()->hook->add(Am_Event::INVOICE_CALCULATE, function(Am_Event $e) {
    if (@$GLOBALS['add_fraction']++) return;
    $invoice = $e->getInvoice();
    $item = $invoice->getItem(0);
    $id = $invoice->pk() ?: $e->getDi()->db->selectCell("SELECT MAX(invoice_id)+1 FROM ?_invoice;");
    if ($item && $item->first_price > 0 && !$item->data()->get('add_fraction')) {
        $item->data()->set('add_fraction', 1);
        $item->data()->set('orig_first_price', $item->data()->get('orig_first_price') + ($id % 1000));
        $invoice->calculate();
    }
    unset($GLOBALS['add_fraction']);
});