Tries to determine whether or not the current user is a search engine spider

Return value

Expected type: Integer
Description: Returns either the ID of the spider that this user appears to be, 0 if they don't appear to be a spider or false if no spiders exist in the DB

• Un-sets $_SESSION['id_robot'] if it's set
• Sets the robot_check session variable to the current timestamp
• Pulls current spider info from the database and caches it if $spider_data isn't set or is null
• Returns false if no spiders exist in the database
• Sets $_SESSION['id_robot'] again if the user appears to be a spider