如何设置默认页面ID？

Question

I am trying to display content depending on page id, however when I add nothing to the url, so just index.php I get an error saying that $p is not defined, how can I give this var a default value that's outside the switch case?

<?php
$p = $_GET['p'];
switch ($p) {
    case 1:
        $content1 = new login();
        $content = $content1->displayLogin();
        break;

    case 2:
        echo "ID is 2";
        break;

    case 3:
        echo "ID is 3";
        break;

    default:
        $content1 = new dbconnection();
        $content = $content1->displayTable();
}

Answer 1

I understand that you want to make $p have a default value if $_GET['p'] is not defined.

You can do it like this:

$p = isset($_GET['p']) ? $_GET['p'] : 'defaultValue';

or, if you're on PHP 7:

$p = $_GET['p'] ?? 'defaultValue';