how to grap value after ' ? '

[eluser]nancy[/eluser]
I passed the return url as
https://www.example.com/barclays/success/($oid)/

but then the payment gateway calls my return url as
https://www.example.com/barclays/success/($oid)/?oid=ADV561549

the error is nothing but its not getting oid and based on that i am fetching data from db.