As YungBlood stated, PHP is a server side technology. The Roku can theoretically act like a regular HTTP client in all aspects, so as long as your site supports normal logins through HTTP/HTML, the Roku could be coded to use that. By HTTP/HTML, I mean core HTTP or HTML, not Javascript, Flash or any other extending technology.
Then again, the recommended way to do this is through linking the player to an account. You can find a few examples in the example code shipped with the SDK .
P.S. The Roku cannot display the webpage, as it has no HTML rendering engine. It can parse the raw HTML and take appropriate action though.
-- GandK Labs
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