Как декодировать такую строку? json_decode() выдает //NULL
$string=array('{["{"id":432067845,"first_name":"Марк","last_name":"Сергеев","is_closed":false,"can_access_closed":true,"sex":2,"bdate":"29_6_1983","city":{"id":1,"title":"Москва"},"country":{"id":1,"title":"Россия"},"photo_100":"https://sun1-84_userapi_com/c855628/v855628666/152ba6/LhxTHnMO9Ys_jpg?ava"]=>
string(104) "1","photo_200":"https://sun1-93.userapi.com/c855628/v855628666/152ba5/-kjl1kGs9Fo.jpg?ava=1","online":1}"');
var_dump(json_decode($string[0])) //Получаю NULL
Как её декодировать?