Using Variables to PHP

So, as you already know Wappler doesn’t have a pdf export function or plugin.

So I’m using fpdf to create pdf files from forms. I have the following php code that should run when the form is submitted.

<?php
require('js/fpdf/fpdf.php');

$pdf = new FPDF();
$pdf->AddPage();
$pdf->SetFont('Arial','B',16);
$pdf->Cell(40,10,'¡Hola, Mundo!');
$filename= //GET FORM WAPPLER FORM//;
//Output the document
$dir = "documents/ArchivosGeneradosUF/"; // full path like C:/xampp/htdocs/file/file/
$pdf->Output($dir.$filename.'.pdf','F');
?>

First question: how do I send the variables from wappler to the php file? (in the code the $filename value should be retreived from the form)

Second question: how do I run that php code (of course sending the data that should be used)