public function logout_class($user_id, $class_id) { if (empty(self::$conn)) { self::$conn = $this->connect_pdo(); } $sql = "DELETE FROM join_class WHERE user_id=? AND class_id=?"; $stmt = self::$conn->prepare($sql); $stmt->bindParam(1, $user_id); $stmt->bindParam(2, $class_id); if ($stmt->execute()) { return true; } else { return false; } }