PHP if else statement testing whether api php field is empty

I am attempting to get the city attribute out of an ip geolocation api. Sample of what is returned from the api:

{"as":"AS38484 Virgin Broadband VISP","city":"Adelaide","country":"Australia","countryCode":"AU","isp":"iseek Communications","lat":-27,"lon":133,"org":"iseek Communications","query":"1.178.0.144","region":"","regionName":"","status":"success","timezone":"","zip":""}

My code:

$query = '{"as":"AS38484 Virgin Broadband VISP","city":"Adelaide","country":"Australia","countryCode":"AU","isp":"iseek Communications","lat":-27,"lon":133,"org":"iseek Communications","query":"1.178.0.144","region":"","regionName":"","status":"success","timezone":"","zip":""}'
$query = @unserialize($query);
if($query && $query['status'] == 'success') {
    if(!empty($query['city'])) {
        $city =  $query['city'];
        // routine that uses $city gets called
    } else {
        $lat = $query['lat'];
        $lon = $query['lon'];
        // routine that uses $lat, $lon gets called
    }
}

Basically, the if(!empty($query['city'])) is not behaving as expected (not that I would really know, I have been using PHP for that last week). I have also attempted setting $city before the if statement and then testing if($city != '').

Note: the reason for the differentiation between city and lat/lon is the weather api I am querying prefers city but not every ip is able to provide one.

Thanks