Laravel\Cashier\Invoice::pdf PHP Method

    public function pdf(array $data)
    {
        if (!defined('DOMPDF_ENABLE_AUTOLOAD')) {
            define('DOMPDF_ENABLE_AUTOLOAD', false);
        }
        if (file_exists($configPath = base_path() . '/vendor/dompdf/dompdf/dompdf_config.inc.php')) {
            require_once $configPath;
        }
        $dompdf = new DOMPDF();
        $dompdf->load_html($this->view($data)->render());
        $dompdf->render();
        return $dompdf->output();
    }

 /**
  * Notify the given user about a new invoice.
  *
  * @param  \Illuminate\Contracts\Auth\Authenticatable  $user
  * @param  \Laravel\Cashier\Invoice  $invoice
  * @return void
  */
 public function notify(Authenticatable $user, Invoice $invoice)
 {
     $invoiceData = array_merge(['vendor' => 'Vendor', 'product' => 'Product', 'vat' => new ViewExpression(nl2br(e($user->extra_billing_info)))], Spark::generateInvoicesWith());
     $data = compact('user', 'invoice', 'invoiceData');
     Mail::send('spark::emails.billing.invoice', $data, function ($message) use($user, $invoice, $invoiceData) {
         $message->to($user->email, $user->name)->subject('Your ' . $invoiceData['product'] . ' Invoice')->attachData($invoice->pdf($invoiceData), 'invoice.pdf');
     });
 }