如何使用PHP迭代JSON？

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

foreach ($data as $key => $value) {
    echo "Key: " . $key . ", Value: " . $value . "<br>";
}

for ($i = 0; $i < count($data); $i++) {
    echo "Index: " . $i . ", Value: " . $data[$i] . "<br>";
}

echo "Name: " . $data->name . "<br>";
echo "Age: " . $data->age . "<br>";
echo "City: " . $data->city . "<br>";

echo "Value at index 0: " . $data[0] . "<br>";
echo "Value at index 1: " . $data[1] . "<br>";
echo "Value at index 2: " . $data[2] . "<br>";