PHP - 使用单选按钮将会话数据传递到另一个页面

I know this question has come up several times.

I read all of the posts and tried them but couldn't get them to work.

I simply want to pass the session data from page 1 to page 2 for a radio button. It won't work no matter what I've tried.

Page 1

<form action="step-2.php" method="post">
    <div class="row">
        <div class="card-left"><img src="card.png" /><br /><input type="radio" name="card" value="card-one" /></div>
        <div class="card-center"><img src="card.png" /><input type="radio" name="card" value="card-two" /></div>
        <div class="card-right"><img src="card.png" /><input type="radio" name="card" value="card-three" /></div>
        <div class="card-right"><img src="card.png" /><input type="radio" name="card" value="card-four" /></div>
    </div>
    <div class="row">
        <div class="card-left"><img src="card.png" /><br /><input type="radio" name="card" value="card-five" /></div>
        <div class="card-center"><img src="card.png" /><input type="radio" name="card" value="card-six" /></div>
        <div class="card-right"><img src="card.png" /><input type="radio" name="card" value="card-seven" /></div>
        <div class="card-right"><img src="card.png" /><input type="radio" name="card" value="card-eight" /></div>
    </div>
    <div class="row">
        <div class="card-left"><img src="card.png" /><br /><input type="radio" name="card" value="card-nine" /></div>
        <div class="card-center"><img src="card.png" /><input type="radio" name="card" value="card-ten" /></div>
        <div class="card-right"><img src="card.png" /><input type="radio" name="card" value="card-eleven" /></div>
        <div class="card-right"><img src="card.png" /><input type="radio" name="card" value="card-twelve" /></div>
    </div>
    <div id="messages">

    <?php

    if($_SERVER['REQUEST_METHOD'] == 'POST') {
        if(isset($_POST["card"])) {
            session_start();
            $_SESSION["card"] == $_POST["card"];
        }


        if(!isset($_POST["card"])) {
            echo '<span style=\"color: red;\">' . "Please choose a card before proceeding" . '</p>';
        } else {

        }

    } else { }

    ?>
    <input type="submit" name="to-step-2" value="Next" id="submit" /></div>
</form>

Page 2 (won't receive and display the data)

<?php

if(isset($_SESSION["card"])) {
    $card = $_SESSION["card"];
    echo $card;
} else {
    echo "<h2>No Card Selected</h2>";
    echo "You didn't select a card. Please go back and select one <a href=\"index.php \">Here</a>";
}

?>

I'm just trying to test this in this state so that I can make sure that the data is being passed and then I will work with the data, but right now it doesn't look like the data is being passed. It instead triggers the default "You didn't select a card" message that I have set up.

At the top of page 2, you need to add session_start(); to resume your session.