Использование JsonUtility с массивом PHP json в единстве

У меня проблемы с использованием JsonUtility и php с json в Unity 5.5.1.

поскольку это показывает ошибку в единстве, говоря это:

ArgumentException: ошибка синтаксического анализа JSON: недопустимое значение.
UnityEngine.JsonUtility.FromJson [ItemDictionary] (System.String json)
(на C: /buildslave/unity/build/artifacts/generated/common/modules/JSONSerialize/JsonUtilityBindings.gen.cs: 24)
DatabaseRead.LoadData (System.String val) (в разделе Активы / Сценарии / DatabaseRead.cs: 40)
DatabaseRead + c__Iterator0.MoveNext () (в разделе Активы / Сценарии / DatabaseRead.cs: 34)
UnityEngine.SetupCoroutine.InvokeMoveNext (перечислитель IEnumerator, IntPtr returnValueAddress)
(в C: /buildslave/unity/build/Runtime/Export/Coroutines.cs: 17)

Код C #:

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;[System.Serializable]
public class Item
{
public string quizid;
public string subject;
public string question;
public string answer;

}

[System.Serializable]
public class ItemDictionary
{
public string[] items;
}

public class DatabaseRead : MonoBehaviour {

public List<Item> items;

IEnumerator Start()
{
WWW questionData = new WWW("localhost/game_dbase/questions.php");
yield return questionData;

string data = questionData.text;

LoadData(data);

}

public void LoadData(string val)
{
ItemDictionary info = JsonUtility.FromJson<ItemDictionary>(val);

foreach (string dictionaryitem in info.items)
{

LoadItem(dictionaryitem);
}
}public void LoadItem(string path)
{
string myLoadedItem = path;
Item myItem = JsonUtility.FromJson<Item>(myLoadedItem);
items.Add(myItem);
Debug.Log(items);
}

}

Код php:

<?php
$servername = @"localhost";
$username =  "root";
$password = "";
$dbName = "game_dbase";

$conn = new mysqli($servername, $username, $password, $dbName);

if(!$conn){
die("Connection Failed. ". mysqli_connect_error());
}

$sql = "SELECT quizid, subjectid, question, answer FROM quiz";
$result = mysqli_query($conn ,$sql);

$json = array();

if(mysqli_num_rows($result) > 0){

while($row = mysqli_fetch_assoc($result)){

$json[]=  array(
'quizid' => $row['quizid'],
'subjectid' => $row['subjectid'],
'question' => $row['question'],
'answer' => $row['answer']
);

}

$jsonstring = json_encode($json);
echo "Items :";
echo $jsonstring;

}
?>

`