Restore radio button selection when revisiting a page - php

Question

I have a PHP script that allows users to enter grades by selecting a radio button that corresponds to the students grade. It allows them to view the selected grades before they can be finally submitted. I also want the page to have the ability to go back to the selection page and remember the radio buttons that were selected so that the user doesn't have to set all of them again when going back. Here is what I have coded so far, it takes the user back to selection page but doesn't restore the radio button selection.
<?php
session_start();
$script_name = $_SERVER["PHP_SELF"];
if(!isset($_SESSION["course"]) || !isset($_SESSION["course"])) {
$_SESSION["course"] = $_POST["coursename"];
$_SESSION["section"] = $_POST["section"];
}
if(($_SESSION["authenticated"] == true || isset($_POST["back"])) && !isset($_POST["continue"])) {
$course = $_SESSION["course"];
$section = $_SESSION["section"];
$file_name = $course.$section.".txt";
$_SESSION["filename"] = $file_name;
// Open file containing student names.
$fp = fopen($_SESSION["filename"], "r") or die("Could not open file");
$students = array();
$i = 0;
echo "<h2>Grades Submission Form</h2>";
echo "<h2>Course: $course, Section: $section</h2>";
echo "<form action=\"$script_name\" method='post'>";
echo "<table border='1'>";
while (!feof($fp)) {
$line = trim(fgets($fp));
$students[$i++] = $line;
echo "<tr><td>$line</td>";
echo "<td><input type='radio' name=\"$line\" value='A'/>A</td>";
echo "<td><input type='radio' name=\"$line\" value='B'/>B</td>";
echo "<td><input type='radio' name=\"$line\" value='C'/>C</td>";
echo "<td><input type='radio' name=\"$line\" value='D'/>D</td>";
echo "<td><input type='radio' name=\"$line\" value='F'/>F</td>";
echo "</tr>";
}
echo "</table><br>";
echo "<input type='submit' name='continue'/>";
echo "</form>";
} elseif($_SESSION["authenticated"] == true && isset($_POST["continue"]) && !isset($_POST["back"])) {
unset($_POST["continue"]);
$keys = array_keys($_POST);
$values = array_values($_POST);
echo "<h2>Grades to Submit</h2>";
echo "<table border='1'>";
echo "<tr><th>Name</th><th>Grade</th></tr>";
for($i = 0; $i < count($keys); $i++) {
echo "<tr><td>{$keys[$i]}</td><td>{$values[$i]}</td></tr>";
}
echo "</table><br>";
echo "<form action='confirmation.php' method='post'>";
echo "<input type='submit' value='Submit Grades'/>";
echo "</form>";
echo "<form action=\"$script_name\" method='post'>";
echo "<input type='submit' value='Back'/>";
echo "</form>";
} else {
header("Location: main.php");
}
?>

Answer 1

You could serialize() an array containing the radio button states and store it in your session. When you go back, all you have to do is unserialize it and set the data again.