I am looking into the mysqli issue for lampp 1.8.0.
PHP 5.4.x uses a different library to support mysqli, new=mysqlnd, old= libmysql. I don't fully understand the impact on lampp at this point.
According to the phpinfo() it appears to have been correctly compiled for the new library
I don't think you need to add the extension/so to the php.ini as they are 'compile withs' - AFAIK that means the code is hard-linked in.
I am seeking wisdom (or correction).
Thanks and good luck