Form URI

[eluser]bondjp[/eluser]
Hi, i'm trying to get my url to show something like this when the user submits a form:

http://example.com/controller/function/city/brand/model

Here's my view:

Code:

<?php
echo form_open('results');
echo form_dropdown('city', $city);
echo form_dropdown('brand', $brand);
echo form_dropdown('model', $model);
<input type="image" src="<?php echo base_url();?>images/search.png"  alt="Submit button" />
echo form_close();

How can i do it?