How to set a default page 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();
}

Possible duplicate of [PHP: "Notice: Undefined variable", "Notice: Undefined index", and "Notice: Undefined offset"](https://stackoverflow.com/questions/4261133/php-notice-undefined-variable-notice-undefined-index-and-notice-undef) — cteski, Mar 19 '18 at 19:13
So really, you're asking how to assign a value to a variable? — Patrick Q, Mar 19 '18 at 19:15
$p = ""; does not work @PatrickQ same for giving it value 0 or 20 (outside switch case) — Eseffe, Mar 19 '18 at 19:16
Read the link in the first comment. You are trying to access an element of an empty array. — waterloomatt, Mar 19 '18 at 19:17
Read your error carefully. Is it saying that the _variable_ `$p` is not defined or is it saying that the _index_ 'p' is undefined? — Patrick Q, Mar 19 '18 at 19:18

dukedevil294 · Answer 1 · 2018-03-19T19:19:36.933

3

Replace:

$p = $_GET['p'];

With:

$p = !empty($_GET['p']) ? $_GET['p'] : default_id_value_here;

edited Mar 19 '18 at 19:19

answered Mar 19 '18 at 19:17

dukedevil294

1,285
17
31

In your replaced line, don't forget to assign that `!empty?` result to $p. – RToyo Mar 19 '18 at 19:18
Good catch. Thanks – dukedevil294 Mar 19 '18 at 19:19

score 3 · Accepted Answer · answered Mar 19 '18 at 19:17

3

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';

answered Mar 19 '18 at 19:17

Phiter

14,570
14
50
84

score 1 · Answer 3 · answered Mar 19 '18 at 19:18

1

You can do the following:

$p = $_GET['p'] ?? <default value>; // e.g 1 or 3 etc.

Read more about it at this question: PHP syntax question: What does the question mark and colon mean?

answered Mar 19 '18 at 19:18

Cyril de Wit

446
4
12

How to set a default page id?

3 Answers3