[SOLVED] global variables

Hi to all,
maybe someone can help my with this one. On my local wamp server I have global variables activated and I can use sessions for one plugin I modified. The plugin in question is restrict-categories and based from which category (when a category is displayed I added a link to post-new.php) the user wants to post a new post it should give him the option to only check one category the post will be added to (basically all other categories are hidden except the one that the post will belong to).
In atahualpa center-column I added this:

session_start();
$eu_scattitle = single_cat_title("", false);
$eu_scatid = get_cat_ID($eu_scattitle);
$eu_curr_cat = get_category($eu_scatid);
$eu_slug=$eu_curr_cat->category_nicename;
$_SESSION['eu_slug'] = $eu_slug; //this is what I need to be stored and later use in restrict-categories

Now, because globals are disabled, the session variable is lost when the execution enters into another .php file.

Is there a way to declare the variable I need inside the center-column (or in one .php file that belongs to atahualpa) and later to be available in the restrict-categories function?... like global $wpdb; or something?

Thank you.