I want to take advantage of template engine i.e. smarty but within my own code
idea is to be able to load TPL file located in Theme's templates folder from within some function (PHP) i.e. get template file content independently from global $template

I tried to

  $template->set_filenames( array('my_content'=>'my_content.tpl') );
  $myvar = $template->parse( 'my_content', true);

but got error that file is not found

I think I may be missing something like tell $template where to look