shopping list

<?php
session_start();

if (!isset($_SESSION['list'])) $_SESSION['list'] = array();

$action = filter_input(INPUT_GET, "action");
if ($action == "clear") {
    $_SESSION['list'] = array();
    header("Location: " . $_SERVER['PHP_SELF']);
}

$shopItem = strip_tags(filter_input(INPUT_POST, "newItem"));
if ($shopItem) array_push($_SESSION['list'], $shopItem);

?><!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8" />
        <title>Shopping list</title>
        <style>td, th {
                padding: 0.2em
            }
        </style>
    </head>
    <body>
        <div id ="shopping">
            <form method ="post">
                <input type="text" name ="newItem" placeholder ="New Item" autofocus />
                <input type ="submit" value="Add" />
            </form>
            <a href="?action=clear">Clear list</a>
            <table>
                <thead>
                    <tr><th>#</th><th>Item</th></tr>
                </thead>
                <tbody>
<?php
foreach ($_SESSION['list'] as $i => $item) echo "\t\t\t\t\t<tr><td>" . ($i + 1) . "</td><td>$item</td></tr>" . PHP_EOL;
?>
                </tbody>
            </table>
        </div>
    </body>
</html>