I tested PHPUnit with the Selenium Server but I can't
test something like login button. If I write for my login
element css=input.login like that $this->click("css=input.login");
but I see the following errors Invalid response while accessing the Selenium Server
and `Value does not implement interface Event.
This turns out to be a Selenium Server bug, solved in the latest version. But this bug still can be encountered in the Netbeans Selenium Server plugin which is using an older version of the server.
In such case unistall the Netabeans plugin, download the server from Selenium website and run it seperatelly. I hope this helps someone. I initially found this solution here: http://www.davidtan.org/netbeans-xampp-phpunit-selenium-all-working-at-last/