用PHP抓取数组索引

Question

我试图从PHP中的数组中获取某个值。

返回的json是

string(3017)"[{"userId":"1","0":"1","order":"[
  {
    \"image\":\"undefined\",\"song\":\"AlwaysNew.mp3\",\"album\":\"Oh No!\"},{\"image\":\"undefined\",\"song\":\"Always1.mp3\",\"album\":\"Fly\"},{\"image\":\"undefined\",\"song\":\"Always2.mp3\",\"album\":\"Album 2\"},{\"image\":\"undefined\",\"song\":\"Always3.mp3\",\"album\":\"Album 1\"},{\"image\":\"undefined\",\"song\":\"Always.mp3\",\"album\":\"Album 4\"},{\"image\":\"undefined\",\"song\":\"AlwaysNew2.mp3\",\"album\":\"Album Title is Unavailable\"},{\"image\":\"undefined\",\"song\":\"AlwaysNew3.mp3\",\"album\":\"Album Title is Unavailable\"}]",
    "1": "[{\"image\":\"undefined\",\"song\":\"AlwaysNew.mp3\",\"album\":\"Oh No!\"},{\"image\":\"undefined\",\"song\":\"Always1.mp3\",\"album\":\"Fly\"},{\"image\":\"undefined\",\"song\":\"Always2.mp3\",\"album\":\"Album 2\"},{\"image\":\"undefined\",\"song\":\"Always3.mp3\",\"album\":\"Album 1\"},{\"image\":\"undefined\",\"song\":\"Always.mp3\",\"album\":\"Album 4\"},{\"image\":\"undefined\",\"song\":\"AlwaysNew2.mp3\",\"album\":\"Album Title is Unavailable\"},{\"image\":\"undefined\",\"song\":\"AlwaysNew3.mp3\",\"album\":\"Album Title is Unavailable\"}]",
    "user_email": null,
    "2": null
  },
  {
    "userId": "2",
    "0": "2",
    "order": "[{\"image\":\"undefined\",\"song\":\"AlwaysNew.mp3\",\"album\":\"Oh No!\"},{\"image\":\"undefined\",\"song\":\"Always1.mp3\",\"album\":\"Fly\"},{\"image\":\"undefined\",\"song\":\"Always2.mp3\",\"album\":\"Album 2\"},{\"image\":\"undefined\",\"song\":\"Always3.mp3\",\"album\":\"Album 1\"},{\"image\":\"undefined\",\"song\":\"Always.mp3\",\"album\":\"Album 4\"},{\"image\":\"undefined\",\"song\":\"AlwaysNew2.mp3\",\"album\":\"Album Title is Unavailable\"},{\"image\":\"undefined\",\"song\":\"AlwaysNew3.mp3\",\"album\":\"Album Title is Unavailable\"}]",
    "1": "[{\"image\":\"undefined\",\"song\":\"AlwaysNew.mp3\",\"album\":\"Oh No!\"},{\"image\":\"undefined\",\"song\":\"Always1.mp3\",\"album\":\"Fly\"},{\"image\":\"undefined\",\"song\":\"Always2.mp3\",\"album\":\"Album 2\"},{\"image\":\"undefined\",\"song\":\"Neville-Peter-Always3.mp3\",\"album\":\"Album 1\"},{\"image\":\"undefined\",\"song\":\"Always.mp3\",\"album\":\"Album 4\"},{\"image\":\"undefined\",\"song\":\"AlwaysNew2.mp3\",\"album\":\"Album Title is Unavailable\"},{\"image\":\"undefined\",\"song\":\"AlwaysNew3.mp3\",\"album\":\"Album Title is Unavailable\"}]",
    "user_email": null,
    "2": null
  }
]" 

我正在使用

解码从我的数据库返回的结果

$order = json_decode($json,true);

它返回

array(2){
  [
    0
  ]=>array(6){
    [
      "userId"
    ]=>string(1)"1"[
      0
    ]=>string(1)"1"[
      "order"
    ]=>string(622)"[{"image":"undefined","song":"AlwaysNew.mp3","album":"OhNo!"},{"image":"undefined","song":"Always1.mp3","album":"Fly"},{"image":"undefined","song":"Always2.mp3","album":"Album2"},{"image":"undefined","song":"Always3.mp3","album":"Album1"},{"image":"undefined","song":"Always.mp3","album":"Album4"},{"image":"undefined","song":"AlwaysNew2.mp3","album":"AlbumTitleisUnavailable"},{"image":"undefined","song":"AlwaysNew3.mp3","album":"AlbumTitleisUnavailable"}]"[
      1
    ]=>string(622)"[{"image":"undefined","song":"AlwaysNew.mp3","album":"OhNo!"},{"image":"undefined","song":"Always1.mp3","album":"Fly"},{"image":"undefined","song":"Always2.mp3","album":"Album2"},{"image":"undefined","song":"Always3.mp3","album":"Album1"},{"image":"undefined","song":"Always.mp3","album":"Album4"},{"image":"undefined","song":"AlwaysNew2.mp3","album":"AlbumTitleisUnavailable"},{"image":"undefined","song":"AlwaysNew3.mp3","album":"AlbumTitleisUnavailable"}]"[
      "user_email"
    ]=>NULL[
      2
    ]=>NULL
  }[
    1
  ]=>array(6){
    [
      "userId"
    ]=>string(1)"2"[
      0
    ]=>string(1)"2"[
      "order"
    ]=>string(622)"[{"image":"undefined","song":"AlwaysNew.mp3","album":"OhNo!"},{"image":"undefined","song":"Always1.mp3","album":"Fly"},{"image":"undefined","song":"Always2.mp3","album":"Album2"},{"image":"undefined","song":"Always3.mp3","album":"Album1"},{"image":"undefined","song":"Always.mp3","album":"Album4"},{"image":"undefined","song":"AlwaysNew2.mp3","album":"AlbumTitleisUnavailable"},{"image":"undefined","song":"AlwaysNew3.mp3","album":"AlbumTitleisUnavailable"}]"[
      1
    ]=>string(622)"[{"image":"undefined","song":"AlwaysNew.mp3","album":"OhNo!"},{"image":"undefined","song":"Always1.mp3","album":"Fly"},{"image":"undefined","song":"Always2.mp3","album":"Album2"},{"image":"undefined","song":"Always3.mp3","album":"Album1"},{"image":"undefined","song":"Always.mp3","album":"Album4"},{"image":"undefined","song":"AlwaysNew2.mp3","album":"AlbumTitleisUnavailable"},{"image":"undefined","song":"AlwaysNew3.mp3","album":"AlbumTitleisUnavailable"}]"[
      "user_email"
    ]=>NULL[
      2
    ]=>NULL
  }
}

当我使用$song = $obj[0]['order'];时，我得到完整的订单字符串：

string(622) "[{"image":"undefined","song":"AlwaysNew.mp3","album":"Oh No!"},{"image":"undefined","song":"Always1.mp3","album":"Fly"},{"image":"undefined","song":"Always2.mp3","album":"Album 2"},{"image":"undefined","song":"Always3.mp3","album":"Album 1"},{"image":"undefined","song":"Always.mp3","album":"Album 4"},{"image":"undefined","song":"AlwaysNew2.mp3","album":"Album Title is Unavailable"},{"image":"undefined","song":"AlwaysNew3.mp3","album":"Album Title is Unavailable"}]" 

哪个好，但有没有办法只获得第一个对象{"image":"undefined","song":"AlwaysNew.mp3","album":"Oh No!"}？

我的PHP代码：

include_once($_SERVER['DOCUMENT_ROOT'].'/wp-load.php' );
$current_user = wp_get_current_user();
$user_email = $current_user->user_email;

$db = new PDO("mysql:hostname=db","root","root");

$st = $db->prepare("SELECT * from wp_songs order by userId");

$st->execute();
$obj = $st->fetchAll();
$json = json_encode($obj);
$order = json_decode($json,true);
$song = $obj[0]['order'];



if ($_POST['submit']) {
        var_dump($song);
}