Correção automática de vencimento de faturas WHMCS

<?php

/*
Hook para WHMCS - Esse hook ajusta automaticamente para segunda-feira as faturas que forem geradas com o vencimento para sábado ou domingo. Inserir na pasta /<sua_pasta_whmcs>/includes/hooks/
*/

function invoiceDuedateCorrection($params) {
    $invoiceId = $params['invoiceid'];
    $invoice = mysql_fetch_assoc(mysql_query("SELECT * FROM tblinvoices WHERE id = " . $invoiceId));
    if(!empty($invoice)) {
        $date = new DateTime($invoice['duedate']);
        $dayNumber = $date->format('N');
        if($dayNumber == '6') {
            mysql_query("UPDATE tblinvoices SET duedate = DATE_ADD(duedate, INTERVAL 2 DAY) WHERE id = " . $invoiceId);
        } elseif($dayNumber == '7') {
            mysql_query("UPDATE tblinvoices SET duedate = DATE_ADD(duedate, INTERVAL 1 DAY) WHERE id = " . $invoiceId);
        }
    }
}


add_hook("InvoiceCreated", 1, 'invoiceDuedateCorrection');