how to pick up requesting url parameters from website address?

Hi All,

I would like to send a customer a link, along the lines of

https://question.com?uid=334444444

which links to a website without any authentication; the landing page is a form, which will display content using a where criteria of the uid from the requesting url.

how can I pick up the url parameters, or just the whole url would do and I could parse it, on loading up this style of website?

David