PHP Session Array values

I am really struggling with a script to pull values out of a session array and then call information from a table in my database.

I can get the values to store in the session no problem and it looks like this when I print it:

Array ( [0] => 17 [1] => 18 [2] => 19 [3] => 20 [4] => 20 [5] => 19 [6] => 17 )

I then have the below PHP to pull the values out of the array and pull the records from my database but it appears to be breaking somewhere and unfortunately I am still quite a noob at PHP.

?php
$action = isset($_GET['action']) ? $_GET['action'] : "";

if($action=='removed'){
    echo "<div> was removed from cart.</div>";
}

if(isset($_SESSION['cart'])){
    $ids = "";
    foreach($_SESSION['cart'] as $id){
        $ids = $ids . $id . ",";
    }

    // remove the last comma
    $ids = rtrim($ids, ',');

    $query = "SELECT * FROM events WHERE EventID IN ({$ids})";
    $stmt = $con->prepare( $query );
    $stmt->execute();

    $num = $stmt->rowCount();

    if($num>0){
        echo "<table border='0'>";//start table

            // our table heading
            echo "<tr>";
                echo "<th class='textAlignLeft'>Product Name</th>";
                echo "<th>Price</th>";
                echo "<th>Action</th>";
            echo "</tr>";

            //also compute for total price
            $totalPrice = 0;

            while ($row = $stmt->fetch(PDO::FETCH_ASSOC)){
                extract($row);

                $totalPrice += $EventCost;

                //creating new table row per record
                echo "<tr>";
                    echo "<td>{$EventID}</td>";
                    echo "<td class='textAlignRight'>{$EventCost}</td>";
                    echo "<td class='textAlignCenter'>";
                        echo "<a href='removeFromCart.php?id={$EventID} class='customButton'>";
                            echo "<img src='images/remove-from-cart.png' title='Remove from cart' />";
                        echo "</a>";
                    echo "</td>";
                echo "</tr>";
            }

            echo "<tr>";
                echo "<th class='textAlignCenter'>Total Price</th>";
                echo "<th class='textAlignRight'>{$totalPrice}</th>";
                echo "<th></th>";
            echo "</tr>";

        echo "</table>";
        echo "<br /><div><a href='#' class='customButton'>Checkout</a></div>";
    }else{
        echo "<div>No products found in your cart. :(</div>";
    }

}else{
    echo "<div>No products in cart yet.</div>";
}
?>

I am assuming its breaking around the query but again I'm still quite a noob at this.

I am trying to pull out all fields in the table but the Primary key I am trying to link to is called 'EventID'. The ID's in the array do actually match the records I am trying to pull out.

I have copied this code from another tutorial site which is why I'm struggling matching it to my own.

Thank you in advance for any help.