pass user id in slug and get user information

The code seems incomplete. Maybe the problem is simply that you define $id but then try to use $user_id? Also, I think id is a protected variable, so maybe use my_id instead.

Try this:

www.mysite.com/test?my_id=123

$user_id = $_REQUEST['my_id'];
$camp_link = get_site_url()."/campaign-detail/?id=".$user_id;
echo "<p class="campaign_store_name"><a href="".$camp_link."">".$camp_title."</a></p>";
$arform_id = Get_ARFORM_ID_using_slug($camp_link);