Get the dynamically created selected radio button value using PHP - php

Question

I am trying to get the selected radio button's value. These values are fetched from a MySQL database bound to the controls. When the program executes, it returns null when I check the selected radio buttons value.
Help is highly appreciated. Thanks in advance.
Snippets of my file are as follows:
HTML:
<form method="POST" action="">
<h3><?php echo $_SESSION['Question'] ?></h3>
<input type="radio" name="radio" value="<?php $_SESSION['Option1'] ?>"><?php echo $_SESSION['Option1'] ?><br/>
<input type="radio" name="radio" value="<?php $_SESSION['Option2'] ?>"><?php echo $_SESSION['Option2'] ?><br/>
<input type="radio" name="radio" value="<?php $_SESSION['Option3'] ?>"><?php echo $_SESSION['Option3'] ?><br/>
<input type="radio" name="radio" value="<?php $_SESSION['Option4'] ?>"><?php echo $_SESSION['Option4'] ?><br/>
</div>
</div>
<div class="row">
<input type="submit" class="btn btn-success" name="button_start" value="Start"/>
<input type="submit" class="btn btn-success" name="button_Back" value="Back"/>
<input type="submit" class="btn btn-success" name="button_save" value="Save"/>
<input type="submit" class="btn btn-success" name="button_Next" value="Next"/>
<input type="submit" class="btn btn-danger" name="button_Submit" value="Submit"/>
</div>
</form>
PHP:
function Save($question_id)
{
if (isset($_POST['button_save'])) {
if (isset($_POST['radio'])) {
$selectedValue = $_POST['radio'];
if (is_null($selectedValue) || $selectedValue == "") {
echo "Please select an option";
} else {
$connectionString = mysqli_connect("localhost", "root", "", "knowellaptitudetest");
if (!$connectionString) {
echo "Error unable to connect to MySQL" . PHP_EOL;
echo "Debugging error no." . mysqli_connect_errno() . PHP_EOL;
echo "Debugging error" . mysqli_connect_error() . PHP_EOL;
exit;
}
if ($selectedValue == $_SESSION['Correct_Answer']) {
//save and update marks for correct ans
$marks = 1;
$query = "INSERT INTO section_marks VALUES('" . $question_id . "','" . $marks . "')";
$result = mysqli_query($connectionString, $query);
$row = mysqli_fetch_row($result, MYSQLI_ASSOC);
$count = mysqli_num_rows($result);
} else {
//save and update marks for wrong answer
$marks = -1;
$query = "INSERT INTO section_marks VALUES('" . $row['Question_ID'] . "','" . $marks . "')";
$result = mysqli_query($connectionString, $query);
$row = mysqli_fetch_row($result, MYSQLI_ASSOC);
$count = mysqli_num_rows($result);
}
mysqli_close($connectionString);
}
}

Answer 1

You have to echo the php variable in html.
<input type="radio" name="radio" value="<?php echo $_SESSION['Option1'] ?>"><?php echo $_SESSION['Option1'] ?><br/>