Dynamic Redirect

I need to be able to have a form submission redirect to a dynamic link. As a for example:

Form
====
Firstname
Lastname
Email
Companyname

Redirect (not form submit)
========
https://someurl.com/page.php?email=Email&first_name=Firstname&last_name=Lastname&company=Companyname

I have been able to handle static redirects easily such as
https://someurl.com/

but I have yet to get a dynamic redirect to work properly.

I apologize if this has been said already, I looked back through several pages but did not go through them all.

and thank you immensely