What does $_GET['key'] return if the key is not set?

Question

What does $_GET return when the index is not set? (Couldn't find anything in php manual about $_GET.)

I wrote this to check, if the $_GET['id'] isset - and if it is not, set $id to false:

<?php $id = (isset($_GET['id'])) ? $_GET['id'] : false ?>

Answer 1

$_GET is just an ordinary array, so it behaves exactly the same as any other array.

This means, it will return NULL to the variable and raise the "undefined index" notice when you call a non-existing index.

The only thing you need to be aware of with $_GET is that is contains unsafe (user-modifiable) data

Answer 2

Unset indexes have the value NULL. Accessing them will result in a notice being raised (unless your error level is set to swallow notices).