Get valule regular expression

Question

I have this regular expression:

company/(.*)-f(\d+).html$ company/view/$2

In view method of company class I use $this->uri->segment(3) to get the value of $2; I can't understand why can't get the value of $2 just like variable.

public function view($param)
{
 echo $param; // no value returned
 $this->uri->segment(3) // works fine
}