passing parameters to controller, please help!

[eluser]Crawley[/eluser]
hello, why can't I pass parameters to my controllers via uri?

Code:

<?php
class Dvd extends Controller {

...

    function dvdinfo($id)
    {
        echo $id;
        
    }

}
?>

now when i load the following uri:

Code:

http://.../index.php/dvd/dvdinfo/123

i get following error:

A PHP Error was encountered

Severity: Warning

Message: Missing argument 1 for Dvd::dvdinfo(), called in .../dvd/system/codeigniter/CodeIgniter.php on line 207 and defined

Filename: controllers/dvd.php

Line Number: 17