Garebooo on "Using $var in condition tags."

Hello,

I am trying to use $var with the condition tags. I have added this code in my theme function file :

is_home(); {
$titles = 'page title';
$description = 'page description';
               }

it's worked fine but, when I repeat the code using is_category, is_single, is_tags ... etc. the $var like ( $titles ) still get the value of is_home. Could anyone please help me to fix this issue.

Thanks in advance,
Mansour