How to customize PHP array for desired JSON output

Question

I have MySQL table named qbank having fields - qid, question_text, subject_id, option_01_text, option_01_is_correct, option_02_text, option_02_is_correct, option_03_text, option_03_is_correct, option_04_text, option_04_is_correct.

My desired JSON output is like this -

[{
        "qid": 5788,
        "question_text": "Which of the following is a traction epiphysis ?",
        "subject_id": 2,
        "options": [{
                "option_code": "A",
                "option_text": "Tibial condyles",
                "option_is_correct": 0
            },
            {
                "option_code": "B",
                "option_text": "Trochanter of femur",
                "option_is_correct": 1
            },
            {
                "option_code": "C",
                "option_text": "Coracoid process of scapula",
                "option_is_correct": 0
            },
            {
                "option_code": "D",
                "option_text": "head of femur",
                "option_is_correct": 0
            }
        ]
    },
    {
        "qid": 5789,
        "question_text": "Which is the most prominent spinous process",
        "subject_id": 2,
        "options": [{
                "option_code": "A",
                "option_text": "T1",
                "option_is_correct": 0
            },
            {
                "option_code": "B",
                "option_text": "C7",
                "option_is_correct": 1
            },
            {
                "option_code": "C",
                "option_text": "C6",
                "option_is_correct": 0
            },
            {
                "option_code": "D",
                "option_text": "L5",
                "option_is_correct": 0
            }
        ]
    }
]

My PHP code is -

$sql = "SELECT * FROM qbank Limit 2";
$query  = $mysqli->prepare($sql);
$query->execute();
$result = $query->get_result();

$output = [];
$options = [];

while ($row = $result->fetch_assoc()) {
    $output[] = [
        "qid"              => $row["qid"],
        "question_text"    => $row["question_text"],
        "subject_id"      => $row["subject_id"],
    ];

    $options[] = [
        "option_code" => "A",
        "option_text" => $row["option_01_text"],
        "option_is_correct" => $row["option_01_is_correct"],
    ];
    $options[] = [
        "option_code" => "B",
        "option_text" => $row["option_02_text"],
        "option_is_correct" => $row["option_02_is_correct"],
    ];
    $options[] = [
        "option_code" => "C",
        "option_text" => $row["option_03_text"],
        "option_is_correct" => $row["option_03_is_correct"],
    ];
    $options[] = [
        "option_code" => "D",
        "option_text" => $row["option_04_text"],
        "option_is_correct" => $row["option_04_is_correct"],
    ];
}
echo json_encode($output, JSON_PRETTY_PRINT);
echo json_encode($options, JSON_PRETTY_PRINT);

The output I am getting from PHP is -

[
    {
        "qid": 5788,
        "question_text": "Which of the following is a traction epiphysis ?",
        "subject_id": 2
    },
    {
        "qid": 5789,
        "question_text": "Which is the most prominent spinous process",
        "subject_id": 2
    }
][
    {
        "option_code": "A",
        "option_text": "Tibial condyles",
        "option_is_correct": 0
    },
    {
        "option_code": "B",
        "option_text": "Trochanter of femur",
        "option_is_correct": 1
    },
    {
        "option_code": "C",
        "option_text": "Coracoid process of scapula",
        "option_is_correct": 0
    },
    {
        "option_code": "D",
        "option_text": "head of femur",
        "option_is_correct": 0
    },
    {
        "option_code": "A",
        "option_text": "T1",
        "option_is_correct": 0
    },
    {
        "option_code": "B",
        "option_text": "C7",
        "option_is_correct": 1
    },
    {
        "option_code": "C",
        "option_text": "C6",
        "option_is_correct": 0
    },
    {
        "option_code": "D",
        "option_text": "L5",
        "option_is_correct": 0
    }
]

My approach was to somehow push $options inside $output, but even after several tries, I am not able to find the correct way.

Nigel Ren · Accepted Answer · 2021-04-17 11:59:52Z

1

You are creating two separate arrays with their own data, you need to build the question and add the options under that question...

while ($row = $result->fetch_assoc()) {
    $question = [
        "qid"              => $row["qid"],
        "question_text"    => $row["question_text"],
        "subject_id"       => $row["subject_id"],
        "options"          => []
    ];

    $question['options'][] = [
        "option_code" => "A",
        "option_text" => $row["option_01_text"],
        "option_is_correct" => $row["option_01_is_correct"],
    ];
    // And other options...

    $options[] = $question;
}
echo json_encode($options, JSON_PRETTY_PRINT);

One other point is that you may find normalizing your database tables useful. So you have a question and answer table. This allows you to have as many (or few) answers per question and stops repeating fields in 1 table.

answered Apr 17, 2021 at 11:59

Nigel Ren

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3 Comments

Dr. Atul Tiwari Over a year ago

Thank you very much for your prompt reply. Earlier in my different attempts, I was making mistake in understanding the concept of using $question['options'][]. Now I got it

Dr. Atul Tiwari Over a year ago

Regarding Normalization of the database table - I read about basic rules of normalization, but I am not able to understand what changes I should make. Can you please point out in short. Thank you once again

Nigel Ren Over a year ago

Have a look at dba.stackexchange.com/questions/23630/…, you may also need something on the answer table to indicate the correct answer, but the principle starts there.

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