PHP 'json_decode‘只适用于第一项

mixed json_decode(string $json, bool $assoc = false, int $depth = 512, int $options = 0)

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

Array
(
    [name] => John
    [age] => 30
    [city] => New York
)

$json = '{"name":"John", "age":30, "city":"New York"}';
$obj = json_decode($json);
echo $obj->name; // 输出：John
echo $obj->age; // 输出：30
echo $obj->city; // 输出：New York

$json = '{"name":"John", "age":30, "address":{"city":"New York", "country":"USA"}}';
$obj = json_decode($json);
echo $obj->name; // 输出：John
echo $obj->age; // 输出：30
echo $obj->address->city; // 输出：New York
echo $obj->address->country; // 输出：USA

$json = '{"name":"John", "description":"This is a \"quoted\" string."}';
$obj = json_decode($json);
echo $obj->name; // 输出：John
echo $obj->description; // 输出：This is a "quoted" string.