The pattern WordPress uses to recognize pages is (.+?), which will match anything, but is not greedy, so it allows you to put something at the end. The following code works for me in WordPress 3.0.1: it places the extra pattern at the second-to-last place of the list, because the final pattern is so generic it will match every URL:
add_filter( 'page_rewrite_rules', 'wpse7243_page_rewrite_rules' );
function wpse7243_page_rewrite_rules( $rewrite_rules )
{
// The most generic page rewrite rule is at end of the array
// We place our rule one before that
end( $rewrite_rules );
$last_pattern = key( $rewrite_rules );
$last_replacement = array_pop( $rewrite_rules );
$rewrite_rules += array(
'(.+?)/([0-9]+)/([^/]+)/([^/]+)/?$' => 'index.php?pagename=$matches[1]&id=$matches[2]&fname=$matches[3]&lname=$matches[4]',
$last_pattern => $last_replacement,
);
return $rewrite_rules;
}
Be aware that pages, like any post, can also be split into multiple pages with the <!--nextpage--> snippet, and the normal URL for that is /pagename/2/, which might be confusing when you also have /pagename/3/jan/fabry/ where the 3 is an ID. You can change the pattern to include an optional page number at the end, so this can become /pagename/3/jan/fabry/2/ where the final 2 is the page number, and the first 3 is the ID.
If you are changing the rewrite rules I recommend my rewrite analyzer plugin (soon in the repository, but get the current version via Dropbox), it helps you debug these things.
