pass variables through url?

[yoyo2]

I've been trying to figure out how to pass variables through the url but have beeen having difficulty. I need to pass variables between servers. do i have the right idea?
thanks.
Many pages:

<a href="http://this.is.my/single/page.php?referrer=here">Link 1</a>

<a href="http://this.is.my/single/page.php?referrer=there">Link 1</a>

The one page:

<?php
if ($GET["referrer"])
{
echo "Referrer: ".$GET["referrer"];
}
else
{
echo "Came without a referral";
}
?>

[mrhappiness]

you're almost right

it's better to check via

if (isset($_GET['referrer']))

[yoyo2]

Is there a simpler way to do this instead of putthing the php code into my index.html page? the reason i ask this is because I need to continue to pass this variable on from page to page until they get to my signup page? any ideas