通过php从json数据中获取一些数据

I have json data which I get from fortigate firewall using api, the data is json data, I want to go through this data and get some info from it. this is the data which I get

array(10) {
 ["http_method"]=>
  string(3) "GET"
  ["results"]=>
   array(2) {
[0]=>
array(14) {
  ["type"]=>
  string(10) "auth_logon"
  ["username"]=>
  string(5) "mihai"
  ["usergroup"]=>
  array(1) {
    [0]=>
    string(5) "mihai"
  }
  ["id"]=>
  int(0)
  ["duration"]=>
  string(11) "123 seconds"
  ["duration_secs"]=>
  int(123)
  ["auth_type"]=>
  int(3)
  ["ipaddr"]=>
  string(10) "10.10.80.1"
  ["src_type"]=>
  string(3) "ip4"
  ["expiry"]=>
  string(13) "28799 seconds"
  ["expiry_secs"]=>
  int(28799)
  ["traffic_vol"]=>
  string(12) "323318 bytes"
  ["traffic_vol_bytes"]=>
  int(323318)
  ["method"]=>
  string(8) "Firewall"
}
[1]=>
array(14) {
  ["type"]=>
  string(10) "auth_logon"
  ["username"]=>
  string(9) "testicafe"
  ["usergroup"]=>
  array(1) {
    [0]=>
    string(9) "testicafe"
  }
  ["id"]=>
  int(0)
  ["duration"]=>
  string(11) "182 seconds"
  ["duration_secs"]=>
  int(182)
  ["auth_type"]=>
  int(3)
  ["ipaddr"]=>
  string(10) "10.10.80.2"
  ["src_type"]=>
  string(3) "ip4"
  ["expiry"]=>
  string(13) "28799 seconds"
  ["expiry_secs"]=>
  int(28799)
  ["traffic_vol"]=>
  string(12) "274990 bytes"
  ["traffic_vol_bytes"]=>
  int(274990)
  ["method"]=>
  string(8) "Firewall"
}
  }
 ["vdom"]=>
  string(4) "root"
  ["path"]=>
  string(4) "user"
   ["name"]=>
   string(8) "firewall"
 ["action"]=>
 string(6) "select"
 ["status"]=>
 string(7) "success"
 ["serial"]=>
 string(16) "FG201E4Q17902047"
 ["version"]=>
 string(6) "v5.6.9"
 ["build"]=>
int(1673)
}

I want to go through this data and retrieve some info like username ,ipaddr and traffic_vol_bytes ,what should I do to get it