PHP variable

Hello,

When I use the following code my browser comes with the following error :
--------------------------------------------------------------------
PHP code:

<?php
if (!$test) echo "test does not exist";
?>
--------------------------------------------------------------------
Browser error:

Notice: Undefined variable: test in d:\www\trash.php on line 3
test does not exist

--------------------------------------------------------------------
But in PHP you don't have to declare a variable
or do I have to ajust some setting in the PHP.ini ????


Thank you,

Frank