use a general variable for all posts

Hi,

I have like this

$SCRurl = "-----------------------";
$VDID ="-----";
$HDDurl = function_name("$SCRurl$VDID");
echo $HDDurl;

and it works
Now I allow other users to make posts in my website
I don’t want them to know what in variable $SCRurl
so I want to put this variable in theme and run this variable in every post
Where should I put this variable ??? In function.php or css or ….
if i can’t ,, is there any way to do this thing by other method

Thanx