WHMCS invoicepdf.tpl mods to save PDF files

<?php

if ($status == 'Paid' || file_exists('/home/whmcs/invoices/' . (int)$invoiceid . '.pdf')) {
    if (get_class($pdf) != 'PDFDecorator') {
        class PDFDecorator {
            protected $_instance;
            public $_invoiceid = 0, $_multi_invoice = 0;

            public function __construct($instance) {
                $this->_instance = $instance;
            }
            public function __get($prop) {
                return $this->_instance->$prop;
            }
            public function __set($prop, $val) {
                return $this->_instance->$prop = $val;
            }
            public function __call($method, $args) {
                return call_user_func_array(array($this->_instance, $method), $args);
            }
            public function Output($name = 'doc.pdf', $dest = 'I') {
                if (!$this->_multi_invoice && $dest == 'S') {
                    if (!file_exists('/home/whmcs/invoices/' . $this->_invoiceid . '.pdf'))
                        $this->_instance->Output('/home/whmcs/invoices/' . $this->_invoiceid . '.pdf', 'F');
                    return file_get_contents('/home/whmcs/invoices/' . $this->_invoiceid . '.pdf');
                }
                return $this->_instance->Output($name, $dest);
            }
        }
        $pdf = new PDFDecorator($pdf);
    }
    if ($pdf->_invoiceid)
        $pdf->_multi_invoice = 1;
    else
        $pdf->_invoiceid = (int)$invoiceid;
}

/* rest of invoicepdf.tpl */