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

Hi,
I'm trying to load an xml file in order to read it's content and print it based on the user logged in. To do so I created a shortcode in functions.php in my child theme folder. Here's the code I wrote:

function dati_tbcrew($atts){
	global $user_login;
	get_currentuserinfo();
	$xml=simplexml_load_file("porva.xml") or die("Error: Cannot create object");
	switch($xml->name['nome']){
		case $user_login: $out=$xml->name->content;break;
		default:break;
	}
	return $out;
}
add_shortcode('dati_tbcrew', 'dati_tbcrew');

Unfortunately when I call the shortcode in a WP page it prints out "Error: Cannot create object". The XML file is in the child theme folder with functions.php. I even tried to put the server folder route in with the file's name in simplexml_load_file but it still isn't working. How can I get it working? Is it even the right procedure? Thanks in advance.