vista1x

function findId($json_data, $cityName) {
  foreach($json_data[$cityName] as $id => $regionName) {
    if ($id < 0) return $id;
  }
}

var_dump(findId($json_data, 'Абакан'));

$json = '{
	"games": [
		{
			"name": "FlatOut 2",
			"image": "http:\/\/www.game-ost.ru\/static\/covers_soundtracks\/1\/1\/11195_599433.jpg",
			"game_key": "DNVI5-74JHP-OLOQ2",
			"start": 1441052980,
			"winner": "https:\/\/vk.com\/id164746581"
		},
		{
			"name": "Anachronox",
			"image": "http:\/\/www.abcgames.sk\/udaje\/cd_obaly\/2\/230_f1.jpg",
			"game_key": "GPXFT-J9GJ4-PF58L",
			"start": 1441114401
		},
		{
			"name": "Daikatana",
			"image": "http:\/\/files.khinsider.com\/vgwallpaper\/1280x1024\/685-daikatana-005-wywlf.jpg",
			"game_key": "GPXFT-J9GJ4-PF58L"
		}
	]
}';


	$data = json_decode($json, true);

	foreach ($data['games'] as $game)
	{
		if (isset($game['winner']))
		{
			//выводим
			print $game['name'] . "<br>";
		}
	}