Your api returns json, you can decode it with json_decode, i have also include how to traverse through the json objects included in the feed.
$json = file_get_contents("http://api.roblox.com/users/3/friends");
$obj = json_decode($json);
for ($i=0; $i < count($obj); $i++) {
echo $obj[$i]->Id;
echo $obj[$i]->Username;
}
3
solved Parsing XML from a Web Page with PHP [closed]