Saving XML file with Joomla module -

i searching while haven't foung single word it. developing joomla module save batch of xml files based on database data. works fine until important moment - saving.

a have in code:

$doc->save("files".$db_id.".xml"); 

and don't work. woudl save generated files speciall folder somewhere, don't know how save root folder of module. possible? , how can it?

thank you.

you can module-file root simple echo in file itself:

<?= __file__ ?> 

then server-root of file , able use returned string save files path.