Handle GET vars from Paypal PDT

[eluser]ecigraeme[/eluser]
Hi,

I want to implement paypal's PDT on a site I am developing. In paypal you specify a URL on your site that paypal will send the user to after payment. Paypal appends a tx code as a GET variable to the URL you specify, which your site then POSTS back to paypal to verify authenticity.

However this gets messed up because of the way codeignitor handles GET variables.
Just by testing these in my browser I see that

http://www.mydomain.com/dev/index.php/paypal/success
works but
http://www.mydomain.com/dev/index.php/pa...ess?tx=123

gives a CI page not found error.

I am using a windows server so do not have an .htaccess to hide the index.php.

Can anybody suggest a way to capture the tx value from paypal without having to change the enable_query_strings setting for the whole site.

Thanks

Graeme