proper way to insert in db?

what is the proper way to insert in other db at registration? In register.php, right after vb insert routine I have been successfully using:

mysql_query("insert into otherdbname.users (userid, uemail, password, user_country) values ('$userid', '$email', '".addslashes(md5($password))."', '$country')");

But since I placed an include in phpinclude, that ceased to work. I had to remove the very important include.