json获取关键名称作为文本？

import json

json_str = '{"name": "John", "age": 30, "city": "New York"}'
json_obj = json.loads(json_str)

for key in json_obj:
    print(key)

const jsonStr = '{"name": "John", "age": 30, "city": "New York"}';
const jsonObj = JSON.parse(jsonStr);

for (const key in jsonObj) {
    console.log(key);
}

import org.json.JSONObject;

String jsonStr = "{\"name\": \"John\", \"age\": 30, \"city\": \"New York\"}";
JSONObject jsonObj = new JSONObject(jsonStr);

Iterator<String> keys = jsonObj.keys();
while (keys.hasNext()) {
    String key = keys.next();
    System.out.println(key);
}

$jsonStr = '{"name": "John", "age": 30, "city": "New York"}';
$jsonObj = json_decode($jsonStr, true);

foreach (array_keys($jsonObj) as $key) {
    echo $key . PHP_EOL;
}