[Pre-populated forms from query string]

Hi,

I am trying to create a form with some hidden fields which become populated with information from the URL.

For example, the URL would be [a href=\"http://www.blahblah.com/form.php?email=client@us.com\" target=\"_blank\"]http://www.blahblah.com/form.php?email=client@us.com[/a]
And from this the email field within the form is populated with their email address.

I think this is quite a simple thing to do but i can't seem to find any examples of it elsewhere. I know how to create a form etc in PHP, but just want to be able to prepopulated fields!

Many many many thanks in advance!!

justin