Array
    (
        [count] => 254
        [items] => Array
            (
                [0] => Array
                    (
                        [id] => 5514668
                        [first_name] => Александр
                        [last_name] => Звягинцев
                        [city] => Array
                            (
                                [id] => 4595
                                [title] => Угледар
                            )

                        [country] => Array
                            (
                                [id] => 2
                                [title] => Украина
                            )

                    )

                [1] => Array
                    (
                        [id] => 8994126
                        [first_name] => Аделина
                        [last_name] => Миронова
                        [city] => Array
                            (
                                [id] => 284
                                [title] => Караганда
                            )

                        [country] => Array
                            (
                                [id] => 4
                                [title] => Казахстан
                            )

                    )

                [2] => Array
                    (
                        [id] => 12290884
                        [first_name] => Даша
                        [last_name] => Аксёненко
                        [country] => Array
                            (
                                [id] => 2
                                [title] => Украина
                            )

                        [hidden] => 1
                    )

                [3] => Array
                    (
                        [id] => 13005009
                        [first_name] => Руслан
                        [last_name] => Адамчик
                        [city] => Array
                            (
                                [id] => 1386
                                [title] => Сергиев Посад
                            )

                        [country] => Array
                            (
                                [id] => 1
                                [title] => Россия
                            )

                    )

                [4] => Array
                    (
                        [id] => 13113031
                        [first_name] => Мария
                        [last_name] => Макарова
                        [city] => Array
                            (
                                [id] => 1
                                [title] => Москва
                            )

                        [country] => Array
                            (
                                [id] => 1
                                [title] => Россия
                            )

                    )

                [5] => Array
                    (
                        [id] => 13730068
                        [first_name] => Александр
                        [last_name] => Чернов
                        [city] => Array
                            (
                                [id] => 73
                                [title] => Красноярск
                            )

                        [country] => Array
                            (
                                [id] => 1
                                [title] => Россия
                            )

                        [hidden] => 1
                    )
             )
      )

foreach ($jsonArray['items'] as $user{
     if($user['city'])
     {
          //если есть поле город
     }
}