Pre-populate a lot of radio button group from database - php

Question

I'm working on a project. I want to pre-populated data from database.
HTML
<div class="question">
<input type="radio" name="q1" value="A" <?php echo $checkedA ?>>
<input type="radio" name="q1" value="B" <?php echo $checkedB ?>>
<input type="radio" name="q1" value="C" <?php echo $checkedC ?>>
</div>
<div class="question">
<input type="radio" name="q2" value="A" <?php echo $checkedA ?>>
<input type="radio" name="q2" value="B" <?php echo $checkedB ?>>
<input type="radio" name="q2" value="C" <?php echo $checkedC ?>>
</div>
<div class="question">
<input type="radio" name="q3" value="A" <?php echo $checkedA ?>>
<input type="radio" name="q3" value="B" <?php echo $checkedB ?>>
<input type="radio" name="q3" value="C" <?php echo $checkedC ?>>
</div>
<!-- etc till let's say 30 question -->
PHP
$query="SELECT * FROM `quiz` WHERE email='$email'";
$result=mysqli_query($link,$query);
$data=mysqli_fetch_assoc($result);
for($i=1; $i<=30; $i++){
switch($data[${"answer".$i}]{
case "A" : $checkedA="checked"; break;
case "B" : $checkedB="checked"; break;
case "C" : $checkedC="checked"; break;
}
}
Then, how to make the q1 which is corresponded with $data['answer1'] checked if it is filled with data from database, etc?

Answer 1

Using the code you've provided, It's viable to get the data from the database and then show the result in your html and not over complicate things. To pre-populate your radio buttons, you need to have the following below:
PHP
$query="SELECT * FROM `quiz` WHERE email='$email'";
$result=mysqli_query($link,$query);
$data=mysqli_fetch_assoc($result);
HTML
<div class="question">
<input type="radio" name="q1" value="A" <?php echo ($data['q1'] == 'A')? 'checked' : ''; ?>>
<input type="radio" name="q1" value="B" <?php echo ($data['q1'] == 'B')? 'checked' : ''; ?>>>
<input type="radio" name="q1" value="C" <?php echo ($data['q1'] == 'C')? 'checked' : ''; ?>>
</div>
<div class="question">
<input type="radio" name="q2" value="A" <?php echo ($data['q2'] == 'A')? 'checked' : ''; ?>>
<input type="radio" name="q2" value="B" <?php echo ($data['q2'] == 'B')? 'checked' : ''; ?>>
<input type="radio" name="q2" value="C" <?php echo ($data['q2'] == 'C')? 'checked' : ''; ?>>
</div>
<div class="question">
<input type="radio" name="q3" value="A" <?php echo ($data['q3'] == 'A')? 'checked' : ''; ?>>
<input type="radio" name="q3" value="B" <?php echo ($data['q3'] == 'B')? 'checked' : ''; ?>>
<input type="radio" name="q3" value="C" <?php echo ($data['q3'] == 'C')? 'checked' : ''; ?>>
</div>
With that piece of code, it sets checked depending on what the value coming from the database is and displays it on the screen.

Answer 2

Example has exactly 3 variables for checked ($checkedA, $checkedB, $checkedC). In order to have 3 varsiables per question, it would need a collection of "checks". If you have n questions, your collection needs n members. And each of those members needs 3 members representing whether the answer is checked, one for each option.
As an example:
If the answer to q1 is A, then
$checked['q1'] = ['A'=> "checked",'B'=>"",'C'=>""].
In the php, initialize a $checked member for each question as described above. Then change the switch to update the corresponding member. [The reason to initialize this way is because 1) everything needs a value in the html and 2) checked is a boolean attribute]
The html would echo $checked[q#]['A'] $checked[q#]['B'] and $checked[q#]['C'] respectively.