Dynamic radio button with self-post using PHP & MySQL - php

Question

I'm drawing data from a MySQL database that dynamically places a question with 4-5 radio button choices for the answer. These radio buttons all belong to the same group, $quest_name. The first pass of the while statement will create 4 radio buttons belonging to radio group "question_1".
It creates 30-40 of these questions on a page, each with 4 radio buttons. I want the user to fill in all there answers and the page to post back to itself with the users answers still selected and then display if they were correct or not (functionality I still have to add).
I'm trying to follow http://www.w3schools.com/php/php_form_complete.asp as an example, but use a dynamically created radio button name instead.
This is what I have thus far:
<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">
<?php
if ($result->num_rows > 0) {
// output data of each row
while($row = $result->fetch_assoc()) {
$quest_num = $row["id"];
$question = $row["question"];
$option_1 = $row["option_1"];
$option_2 = $row["option_2"];
$option_3 = $row["option_3"];
$option_4 = $row["option_4"];
$option_5 = $row["option_5"];
$answer = $row["answer"];
$quest_name = "question_" . $row["id"];
echo "(" . $quest_num . ") " . $question . "<br>";
?>
<label>
<input type="radio" name=<?php echo $quest_name ?>
<?php if (isset(echo $quest_name) && echo $quest_name == echo $option_1) echo "checked"; ?>
value=<?php echo $option_1 ?>><?php echo $option_1 ?>
</label>
<br>
<label>
<input type="radio" name=<?php echo $quest_name ?>
value=<?php echo $option_2 ?>><?php echo $option_2 ?>
</label>
<br>
<label>
<input type="radio" name=<?php echo $quest_name ?>
value=<?php echo $option_3 ?>><?php echo $option_3 ?>
</label>
<br>
<label>
<input type="radio" name=<?php echo $quest_name ?>
value=<?php echo $option_4 ?>><?php echo $option_4 ?>
</label>
<br>
<br>
<?php
}
} else {
echo "0 results";
}
$conn->close();
?>
<input type="submit">
</form>
The part causing me grief so far is:
<?php if (isset(echo $quest_name) && echo $quest_name == echo $option_1) echo "checked"; ?>
I have also tried:
<?php if (isset($quest_name) && $quest_name == $option_1) echo "checked"; ?>
and:
<?php echo (isset($quest_name) && $quest_name == $option_1) ? "checked" : ""; ?>
How do you post back to the same page what they've selected? Like in this case I'm trying to say if "question_1" is set and "question_1" is equal to "converter" (the first radio button option) then have it checked when submit button is clicked.
I'm not that good at web development, but I'm trying to create a website to help my fellow electrical technician classmates.
Thanks for any help.
EDIT :
Using this line of code fixed the issue:
<?php if(isset($_POST[$quest_name]) && $_POST[$quest_name]==$option_1) { echo 'checked="checked"'; } ?>

Answer 1

What you need is called Radio Group. In HTML layer it is created with same name for all and different values for each like this:
<p>
<label>
<input type="radio" name="RadioGroup1" value="Value1" id="RadioGroup1_0">
Radio</label>
<br>
<label>
<input type="radio" name="RadioGroup1" value="Value2" id="RadioGroup1_1">
Radio</label>
<br>
</p>
And when you want to get the user input in php layer you go like this:
<?php
//check if Radio Group 1 is set
if(isset($_POST['RadioGroup1'])) {
// print the value of Radio Group 1 choice
echo $_POST['RadioGroup1'];
}
?>
When you want to create a Selected Radio in HTML layer you go like this:
<input name="RadioGroup1" type="radio" id="RadioGroup1_1" value="radio" checked="checked">
So you have to check if user inputs the value of which radio like this:
<label>
<input type="radio" name="RadioGroup1" value="value1" id="RadioGroup1_0" <?php if(isset($_POST['RadioGroup1']) && $_POST['RadioGroup1']=='value1') { echo ' checked="checked"'; } ?>>
Radio</label>
<br>
<label>
<input type="radio" name="RadioGroup1" value="value2" id="RadioGroup1_1" <?php if(isset($_POST['RadioGroup1']) && $_POST['RadioGroup1']=='value2') { echo ' checked="checked"'; } ?> >
Radio</label>

Answer 2

You could use the following:
<input type="radio" name="<?php echo $quest_name ?>" value="<?php echo $option_1 ?>"
<?php if (isset($quest_name) && ($quest_name == $option_1)) echo "checked"; ?> />