PHP XMLWriter custom 'doctype'

Question

How do I replicate the following with PHP XMLWriter();

<?qbxml version="12.0"?>

I tried doing the following but could replicate the second ? at the end.

$writer->startElement("?qbxml");  
   $writer->writeAttribute('version', '12.0'); 

Answer 1

According to the manual:

$writer->writePI("qbxml", 'version="12.0"');