How to customize PDF of Invoice Notification

For example, to add a Boleto/Pix code at the PDF, you just need to overwrite the method getInvoicePdfUrlByInvocieId in the notification class. This method is used by the module to create the PDF of the invoice to be sent to the client.

// ...

use setasign\Fpdi\Fpdi;

final class InvoiceReminderPdfNotification extends AbstractWhatsAppNotifcation
{
    public string $notificationCode = 'InvoiceReminderPdf';

    public function run(): bool
    {
        // ...
    }

    public static function getInvoicePdfUrlByInvocieId(int $id, bool $returnNullOtherwise = false): ?string
    {
        require_once __DIR__ . '/../../../../../../../includes/invoicefunctions.php';

        // 1. Generate the invoice PDF using WHMCS built-in function.
        $whmcsInvoicePdf = pdfInvoice($id);


        $randonPrefix = (string) (random_int(0, 100000));
        $randomFileName = uniqid($randonPrefix, true) . '.pdf';

        $pdfPath = __DIR__ . "/../../../resources/temp/invoices_pdf/$randomFileName";

        // 2. Save the WHMCS-generated PDF to be able to edit it after.
        $wasInvoicePdfSaved = file_put_contents($pdfPath, $whmcsInvoicePdf);

        if (!$wasInvoicePdfSaved) {
            throw new Exception('Could not create invoice PDF: ' . $wasInvoicePdfSaved);
        }

        // 3. Use fpdi to edit the PDF.

        /**
         * @see https://manuals.setasign.com/fpdi-manual/v1/the-fpdi-class/examples/
         */
        $pdfEditorInstance = new Fpdi();

        $pageCount = $pdfEditorInstance->setSourceFile($pdfPath);

        for ($i = 1; $i <= $pageCount; $i++) {
            $tplId = $pdfEditorInstance->importPage($i);

            $pdfEditorInstance->AddPage();
            $pdfEditorInstance->useTemplate($tplId);
        }

        // 4. Insert a new page at the end of the PDF.

        $pdfEditorInstance->setSourceFile($pdfPath);
        $pdfEditorInstance->AddPage();
        $pdfEditorInstance->SetFont('Helvetica', '', 12);
        $pdfEditorInstance->SetXY(12, 12);

        // 4.1 Insert any text. At the pointm you can use Capsule::table() to retrieve data from the Database
        // and insert in the PDF.

        $textToAdd = 'Pix Copia e Cola!!!';

        $pdfEditorInstance->Cell(0, 10, $textToAdd);

        $pdfEditorInstance->Output('F', $pdfPath);

        $invoicePdfUrl = Link::moduleUrl() . "/src/resources/temp/invoices_pdf/$randomFileName";

        return $invoicePdfUrl;
    }

    public function defineParameters(): void
    {
        $this->parameters = [
            'invoice_pdf_url' => [
                'label' => $this->lang['invoice_pdf_url'],
                'parser' => fn () => self::getInvoicePdfUrlByInvocieId($this->hookParams['invoiceId'])
            ],
        ];
    }
}