如何使用PHP提取特定的JSON元素？

$jsonString = '{"name":"John", "age":30, "city":"New York"}';
$data = json_decode($jsonString);

// 访问数组元素
$name = $data['name'];
$age = $data['age'];

// 访问对象属性
$name = $data->name;
$age = $data->age;

$jsonString = '{"person":{"name":"John", "age":30, "city":"New York"}}';
$data = json_decode($jsonString);

// 访问嵌套元素
$name = $data->person->name;
$age = $data->person->age;

$jsonString = '[{"name":"John", "age":30, "city":"New York"}, {"name":"Jane", "age":25, "city":"London"}]';
$data = json_decode($jsonString);

// 提取多个元素
foreach ($data as $item) {
    $name = $item->name;
    $age = $item->age;
    // 其他操作...
}