I worked on something similar a couple of weeks ago, but I took a different approach. By breaking up the architecture into several layers, you can test individual pieces without having to write tests to submit and to parse HTML.

For example, I had a handful of routines that had to validate, insert, and select data from a database. For my tests, I used a CSV file and passed in a DBI connection using DBD::CSV. Then all I had to do was write tests for the methods, and I could validate them there.

If the highest architecture layer only ever presents the final interface, you can get by with very little testing there, and write simple automated tests for all of the other layers.

Of course, with PHP it may be harder to separate things out, but the same principle should apply.