Using SimpleXml in PHP and converting to an Object

I am struggling a bit with getting the values from my XML feed using Simplexml.

I am using this to get the XML into an object:

$this->adObj = simplexml_load_string(file_get_contents($url));

However, I am struggling to get the values.

For example, these are actually product feeds from a 3rd party. When I use var_dump I can see $obj->Products->Product which is actually an array of products but if I try and get the values from the first array I get a blank page.

$obj->Products->Product[0]->Offer->Url and this returns a blank page?

Here is a snipplet of the var_dump. I think I am making a mistake somewhere when I select a specific array using "[0]". Any help or advice appreciated.

object(SimpleXMLElement)#2 (2) {
["Products"]=>
object(SimpleXMLElement)#3 (2) {
["@attributes"]=>
array(3) {
["firstResultPosition"]=>
string(1) "1"
["totalResultsAvailable"]=>
string(5) "31576"
["totalResultsReturned"]=>
string(3) "100"
}
["Product"]=>
array(100) {
[0]=>
object(SimpleXMLElement)#5 (2) {
["@attributes"]=>
array(1) {
["type"]=>
string(5) "Offer"
}
["Offer"]=>
object(SimpleXMLElement)#105 (14) {
["@attributes"]=>
array(1) {
["id"]=>
string(32) "0edea796f13547724c949f93247ca113"
}
["Url"]=>
string(270) "http://uk.shoppingapis.kelkoo.com/ctl/go/sitesearchGo?.ts=1267485724046&.sig=eZJrCjf4u03RufQ0DcS7Q.zyeZ4-&offerId=0edea796f13547724c949f93247ca113&searchId=87248117221_1267485724041_24181632&affiliationId=96928412&country=uk&wait=true&ecs=ok&comId=532601&catId=100020213"