Where do I define index?

php

Solution

You can first check to see if it has been set:

if (isset($_GET["id"])) {

    if ($_GET["id"] == "1") {

    } elseif ($_GET["id"] == "2") {

    }

}

isset is a language construct which will not issue any errors if the variable isn't set.

empty also won't issue errors but also checks for a "non-empty" value.

Problem

`index.php` contains links in this style: ``` <a href="index.php?id=1">1</a> <a href="index.php?id=2">2</a> ``` and then a PHP passage in this style: ``` if ($_GET["id"] == "1") {} elseif ($_GET["id"] == "2") {} ``` So when a link is clicked, the page is reloaded, and one of the if/elseif blocks is run. However, when I load `index.php` the first time I get this error: Undefined index: id I guess this means that `$_GET["id"]` needs to have a default value. But where do I put this default value in my code? If I give it, for example, the value `"0"` in the beginning of the script, the code blocks will never run, since the value keeps being reset on every reload.

Original source