具有特定输出的JSON编码

Question

我正在尝试将数据库查询的输出显示为多选测验程序的特定JSON输出。我调试了脚本，它工作正常，但我需要将多维数组的结果显示为下面显示的JSON输出格式：

{"childItems":[

        {"itemId":"question1", "itemType":"BT_questionItem", 
        "questionText":"What is the capital city of Nevada?", 
        "correctAnswerText":"Carson City", 
        "incorrectText1":"Las Vegas", 
        "incorrectText2":"Reno", 
        "incorrectText3":"Tahoe", 
        "imageURLSmallDevice":"http://www.mywebsite.com/quizImage1.png", 
        "imageURLLargeDevice":"http://www.mywebsite.com/quizImage1.png" 
        },

        {"itemId":"question2", "itemType":"BT_questionItem", 
        "questionText":"What is the capital city of California?", 
        "correctAnswerText":"Sacramento", 
        "incorrectText1":"Modesto", 
        "incorrectText2":"Monterey", 
        "incorrectText3":"Los Angeles", 
        "imageURLSmallDevice":"http://www.mywebsite.com/quizImage2.png",
        "imageURLLargeDevice":"http://www.mywebsite.com/quizImage2.png"
        }

    ]
}

现在这里是我的代码（我留在调试行中供其他人使用，如果他们也需要它们）：

<?php    
    if(!$connection)
    {
        die('Unable to connect to database server.');
    }
    if(!mysql_select_db($dbname, $connection))
    {
        die('Unable to select database.');
    }

    //Query for questions/answers
    $question_table="wp_mtouchquiz_question";
    $answer_table="wp_mtouchquiz_answer";

    $query = "SELECT q.id, q.question, a.answer
    FROM {$question_table} q
    JOIN {$answer_table} a ON q.ID = a.QUESTION_ID
    WHERE q.quiz_id = 1
    ORDER BY question_id ASC, correct DESC";
    $result = mysql_query($query);
    ## DEBUGGING LING ##
    echo "Query: {$query}<br>
    Num Records " . mysql_num_rows($result) . "<br><br>\n";
    if(!$result)
    {
        //die ('Unable to get questions.'); //Comment out to debug
        die("Query: $query<br>Error: " . mysql_error());
    }
    //Populate results into multi-dimensional array
    $questions = array();
    while($row = mysql_fetch_assoc($result))
    {
        ## DEBUGGING LING ##
        echo implode(" : ", $row) . "<br>\n";
        $qID = $row['id'];
        if(!isset($questions[$qID]))
        {
            $questions[$qID] = array(
                                     'question'    => $row['question'],
                                     'question_id' => $qID,
                                     'answers'     => array()
                                     );
        }
        $questions[$qID]['answers'][] = $row['answer'];
    }

    ## DEBUGGING LING ##
    echo "Array before randomizing:<br><pre>" . print_r($questions, true) . "</pre><br>\n";

    //Randomize the questions and answers
    shuffle($questions);
    foreach($questions as &$question)
    {
        unset($question['answers'][rand(1, 4)]); // <== This will remove one of the incorrect answers before randomizing
        shuffle($question['answers']);
    }

    ## DEBUGGING LING ##
    echo "Array after randomizing:<br><pre>" . print_r($questions, true) . "</pre><br>\n";

    //NOW output the results in the needed JSON string

    ?>