Nested SOQL Query in PHP

I've the following SOQL query in PHP

SELECT Id, Contact.Account.Name, CommunityNickname FROM User where CommunityNickname != ''

That returns an sObject, however, when I try to retrieve the fields I get:

Notice: Use of undefined constant Account - assumed 'Account' in /opt/bitnami/apache2/htdocs/consent_pbform_generator.php on line 59

Notice: Use of undefined constant Name - assumed 'Name' in /opt/bitnami/apache2/htdocs/consent_pbform_generator.php on line 59

The code I'm using to get the fields is:

$id = $sObject->Id;
$name = $sObject->fields->Contact.Account.Name;
$nickname = $sObject->fields->CommunityNickname;

And this is an echo of the sObject:

stdClass Object
(
    [type] => User
    [Id] => Array
    (
        [0] => 005j000000BvehhAAB
        [1] => 005j000000BvehhAAB
    )

[any] => Array
    (
        [Contact] => stdClass Object
            (
                [type] => Contact
                [Id] => 
                [any] => Array
                    (
                        [Account] => stdClass Object
                            (
                                [type] => Account
                                [Id] => 
                                [any] => Paddy Test
                            )

                    )

            )

        [0] => paddy.test
    )

)

I can't seem to get to reference just the value of Contact.Account.Name or CommunityNickname.

The query works fine in the Dev Console.

Paddy