/* Function to check if the user is blocked */ function is_block($user_id) { // Code to check the user's block status from the database // Return true if user is blocked, false otherwise } // Call the is_block function to check if the user is blocked $user_id = 123; if(is_block($user_id)) { echo "Sorry, you are currently blocked from accessing this site."; } else { // Continue with business logic }The package library for PHP user authentication and access control systems might be something like "PHPAuth" or "Sentinel".