php REQUEST_URI

You can either use regex, or keep on using str_replace.

Eg.

$url = parse_url($_SERVER['REQUEST_URI']);

if ($url != '/') {
    parse_str($url['query']);
    echo $id;
    echo $othervar;
}

Output will be: http://www.testing.com/123/123

perhaps

$id = isset($_GET['id'])?$_GET['id']:null;

and

$other_var = isset($_GET['othervar'])?$_GET['othervar']:null;

You can simply use $_GET especially if you know the othervar's name. If you want to be on the safe side, use if (isset ($_GET ['varname'])) to test for existence.

I think that parse_str is what you're looking for, something like this should do the trick for you:

parse_str($_SERVER['QUERY_STRING'], $vars);

Then the $vars array will hold all the passed arguments.