如何使用PHP将MySQL数据转换为JSON嵌套数组

Question

I want to convert the MySQL data using PHP in table called tbl_questions to JSON and the result of JSON will be like this :

{
"allRoundData": [{
    "name": "Animals",
    "timeLimitInSeconds": 20,
    "pointsAddedForCorrectAnswer": 10,
    "questions": [{
        "questionText": "Lions are carnivores: true or false?",
        "answers": [{
            "answerText": "True",
            "isCorrect": true
        }, {
            "answerText": "False",
            "isCorrect": false
        }]
    }, {
        "questionText": "What do frogs eat?",
        "answers": [{
            "answerText": "Pizza",
            "isCorrect": false
        }, {
            "answerText": "Flies",
            "isCorrect": true
        }]
    }, {
        "questionText": "Where do mice live?",
        "answers": [{
            "answerText": "In the sea",
            "isCorrect": false
        }, {
            "answerText": "On the moon",
            "isCorrect": false
        }, {
            "answerText": "On land",
            "isCorrect": true
        }, {
            "answerText": "In a tree",
            "isCorrect": false
        }]
    }]
}]

}

And how kind table I've to create to handle all these data ?