FebzPD on "load custom xml file to be used in wordpress page"

I tried both like this:

$percorso=get_stylesheet_directory_uri();
	$percorso.="porva.xml";
	$xml=simplexml_load_file($percorso) or die("Error: Cannot create object");

and like this:

$percorso=get_stylesheet_directory();
	$percorso.="porva.xml";
	$xml=simplexml_load_file($percorso) or die("Error: Cannot create object");

Still returns the "Error:..." string in both cases.