Url segment in ci4

In a controller:

$segment =  $this->request->uri->getSegment(1);

Thank you. This worked brilliantly.

I'm still relatively new to CI4, but the CI documentation does not explain segments well at all. The documentation says:

URI Segments

Each section of the path between the slashes is a single segment. The URI class provides a simple way to determine what the values of the segments are. The segments start at 1 being the furthest left of the path.

Code:

// URI = http://example.com/users/15/profile

// Prints '15'
if ($request->uri->getSegment(1) == 'users')
{
        echo $request->uri->getSegment(2);
}

 

But I cannot get the documentation's explanation working. The closest I got was an 'Out of range' error.