Duplicated data entries in PHP array

Question

I'm not sure if this appropriate on here since it is more of a understanding issue on my part but I''m curious to know why I receive this output:

Response id: 3 Question id: 1 Question: What is my middle name? Title: How Well Do You Know Michael
Array ( [0] => Array ( [0] => 3 [r_id] => 3 [1] => 1 [question_id] => 1 [2] => What is my middle name? [question] => What is my middle name? [3] => How Well Do You Know Michael [title] => How Well Do You Know Michael ) ) 

when I run this PHP script:

// Grab the response data from the database to generate the form
    $query = "SELECT qr.response_id AS r_id, qr.question_id, q.question, quiz.title " . 
         "FROM quiz_response AS qr " . 
         "INNER JOIN question AS q USING (question_id) " . 
         "INNER JOIN quiz USING (quiz_id) " .
         "WHERE qr.user_id = '" . $_SESSION['user_id'] . "'";
    $data = mysqli_query($dbc, $query) or die("MySQL error: " . mysqli_error($dbc) . "<hr>\nQuery: $query");
    $questions = array(); 
    while ($row = mysqli_fetch_array($data)) {
        echo 'Response id: ' . $row['r_id'] . 'Question id: ' . $row['question_id'] . ' Question: ' . $row['question'] . ' Title: ' . $row['title'] . '<br />';
        array_push($questions, $row);
    }
    print_r($questions);

It seems as though there are two entries for each piece of data. For example, there are two entries of the 'Response id' under index [0] and [r_id]. Both equal 3. Is it a delirious fear of mine worrying about duplicated data in my array? I'm thinking of the future when I'm doing 10's of queries at a time and whether this will affect speed or accuracy. Any input is greatly appreciated!

Answer 1

If you check out the documentation of mysqli_fetch_array you see the second parameter $result_type which is by default set to MYSQL_BOTH.

That means both the numerical field index (MYSQL_NUM) and the field name (MYSQL_ASSOC) are used as array-index. So if you only need the field name indices you have to use it like that:

while ($row = mysqli_fetch_array($data, MYSQL_ASSOC)) {
    // ....