How to get an empty parameter from an url like “ex

Question

I am using symfony 1.0 and below is the URL which displays the news description.

http://news4u.com/search/news/id/344158/css//act/n

In the above URL value for CSS is missing and the URL is supposed to be as below

http://news4u.com/search/news/id/344158/css/n/act/n

When I use $this->getRequestParameter('css') to get the value of css, I get it as 'act' and if the do the same for 'act', I get empty value.

$getRequestParameter('css')=act
$getRequestParameter('act')=<EMPTY>

I am getting values for above parameters for the metioned URL.

I want to get value of 'act' in above URL. How to get that?