Найти значение по ключу и изменить значение в массиве

$json = '{
        "id": 2,
        "firstName": "Тест",
        "lastName": "Тест",
        "patronymic": "Тест",
        "sexId": 101252,
        "mobilePhone": "71111111111",
        "registrationNumber": {
            "id": 6,
            "seria": "",
            "no": "",
            "extraNumber": "",
            "issueDate": null,
            "closeDate": null,
            "manager": "",
            "subdivisionCode": "",
            "complementaryDocTypeId": null
        },
        "personRelatives": [
            {
                "id": 4,
                "lastName": "dsv",
                "firstName": "sd",
                "patronymic": "",
                "resident": false,
                "passport": {
                    "id": 43,
                    "seria": "",
                    "no": "",
                    "extraNumber": null,
                    "issueDate": null,
                    "closeDate": null,
                    "manager": "",
                    "subdivisionCode": "",
                    "complementaryDocTypeId": null
                },
                "rnn": "",
                "telephone": "",
                "email": "",
                "workPlace": "",
                "address": "",
                "birthDate": null,
                "collateralRelId": 102147,
                "verified": null,
                "comments": ""
            }
        ],
        "clientRiskStatus": [
            {
                "id": 5,
                "insertDate": 1539244552517,
                "userId": 1027,
                "comments": "3211",
                "valueId": 102184
            },
            {
                "id": 8,
                "insertDate": 1540396776913,
                "userId": 1027,
                "comments": "321",
                "valueId": 102184
            },
            {
                "id": 9,
                "insertDate": 1540397890848,
                "userId": 1027,
                "comments": "123",
                "valueId": 102184
            },
            {
                "id": 10,
                "insertDate": 1540398177463,
                "userId": 1027,
                "comments": "вшозавц",
                "valueId": 102184
            },
            {
                "id": 11,
                "insertDate": 1540398590878,
                "userId": 1027,
                "comments": "авлоавыолз",
                "valueId": 102184
            },
            {
                "id": 2,
                "insertDate": 1539067291379,
                "userId": 1027,
                "comments": "Новый клиент",
                "valueId": 102185
            }
        ],
        "extraFields": [
            {
                "id": 178,
                "key": "placeOfEducation",
                "value": "kzt1"
            },
            {
                "id": 179,
                "key": "work1",
                "value": "workk1"
            },
            {
                "id": 180,
                "key": "work2",
                "value": null
            },
            {
                "id": 181,
                "key": "work3",
                "value": null
            },
            {
                "id": 182,
                "key": "placeOfEducation1",
                "value": "kzt1"
            },
            {
                "id": 183,
                "key": "work6",
                "value": ""
            }]}';
$json = json_decode($json, true);

var_dump($json['extraFields']);
foreach($json['extraFields'] as $key => $val){
    if($val['key'] == "work1"){ // находим нужный ключ
        $json['extraFields'][$key]['value'] = 'new your value'; // меняем значение на нужное в исходном массиве
    }
}
var_dump($json['extraFields']);

Результат

 //было
[1]=>
  array(3) {
    ["id"]=>
    int(179)
    ["key"]=>
    string(5) "work1"
    ["value"]=>
    string(6) "workk1"
  }
 // стало
[1]=>
  array(3) {
    ["id"]=>
    int(179)
    ["key"]=>
    string(5) "work1"
    ["value"]=>
    string(14) "new your value"
  }