Redirect page within a plugin

Hey everyone, I’m working on a plugin with a simple form. When the form is submitted, I would like to redirect the user to another page with a PHP header, like:
header(‘Location: https://www.mysite.com/thankspage’);

Of course, I run into the “Headers already sent” error, since all WordPress pages include include output of one type or another at the top of the page.

Is there any standard way of redirecting to a page within WordPress?

Any help would be appreciated.