如何使用PDO通过此语句获取数据并仅检索第一列？

As the title states, I am only able to grab the id column, I am getting an Undefined index error for the others.

My code:

if(isset($_SESSION['id'])) {
    $presh = $_SESSION['id'];
    $stmt = $pdo->prepare("SELECT id FROM users WHERE id = :id");
    $id = $presh;
    $stmt->execute(array(':id'=>$id));
    $accountinfo = $stmt->fetch(PDO::FETCH_ASSOC);
}

Later on in my code I reference it as such:

Karma <span id="kcurrent"><?php echo $accountinfo["karmacurrent"]; ?></span> | <span id="ktotal"><?php echo $accountinfo["karmatotal"]; ?></span>

The rows do exist and they are filled, what am I doing wrong?

You can only select the id column because that is all you have in the query.

Try something like this

if (isset($_SESSION['id'])) {
    $presh = $_SESSION['id'];
    $stmt = $pdo->prepare("SELECT id, karmacurrent FROM users WHERE id = :id");

    $id = $presh;

    $stmt->execute(
        array(
            ':id'=>$id
        )
    );

    $accountinfo = $stmt->fetch(PDO::FETCH_ASSOC);
}

Basically you were only retrieving the ID from the table instead of the other columns.