mkdir php TCPDF ERROR

Question

I have an application that generates a pdf file and saves it in a specific directory. I followed the steps of the php manual(http://php.net/manual/en/function.mkdir.php) for use of this function.

I’ve already given permission as sudo(runs on a Ubuntu server with Nginx)but I keep getting the same error return.TCPDF ERROR: Unable to create output file This error is generated because after creating and saving, the file must be downloaded, but as the file is not being generated I have this return error.

Row:

$html2pdf->Output('./modelos/docs/'.'.pdf', 'F');
$modelObj->add_file($dados['id'], './modelos/docs/'.'.pdf', "Regulamento");
$html2pdf->Output('regulamento_'.$dados['id'].'.pdf', 'D');