Phpmail Help?

[six]

Hi, I'm sending an email in php, and would like to include some dynamic values in the email, but for some reason it's not picking it up, so when u get the email it just looks like $NickName,

my code:

$NickName = $_REQUEST['NickName'];
$message = 'Thank you, $NickName for pre-registering';

could someone show me the correct syntax to make this work?

thanks in advance for your time!
-Ken