Yep, that code should work, provided you have the correct string in the 2nd part of the strpos-function. Do take into account that PHP's $_SERVER["REQUEST_URI"] does not contain the full URL, but rather the path. So if the URL you want to exclude is http://domain.net/page/this-is-page-B, then you should match on "this-is-page-B" (or "B" or "page-B" or ...).
frank