DRY example 1

dry.example.1.php

function calculateInvoiceTotal(Invoice $invoice): float
{
    $mainTotal = 0;
    foreach ($invoice->main->items() as $item) {
        if ($item->revoked() !== true) {
            $mainTotal = $mainTotal + $item->total();
        }
    }
    
    $othersTotal = 0;
    foreach ($invoice->others->item() as $item) {
        if ($item->revoked() !== true) {
            $othersTotal = $othersTotal + $item->total();
        }
    }
    return $mainTotal + $othersTotal;
}