<p>I'm starting to learn how to use PHPUnit to test the website I'm working on.  The problem I'm running into is that I have five different user types defined and I need to be able to test every class with the different types.  I currently have a user class and I would like to pass this to each function but I can't figure out how to pass this or test the different errors that could come back as being correct or not.</p>

<p><b>Edit:</b> I should have said.  I have a user class and I want to pass a different instance of this class to each unit test. </p>

If you're looking to test the actual UI, you could try using something like Selenium (www.openqa.org). It lets you write the code in PHP (which I'm assuming would work with phpUnit) to drive the browser..
Another approach would be to have a common method that could be called by each test for your different user type. ie, something like 'ValidatePage', which you could then call from TestAdminUser or TestRegularUser and have the method simply perform the same basic validation of what you're expecting..