Xampp: SQLSTATE[HY000] [2002] Invalid argument

I'm currently developing a web application using Zend Framework 1.9.x. For this purpose I used Xampp for linux (i.e. lampp 1.7.2). Most of the time I was using arch linux with xampp 1.7.2 and there was no problem. Then I changed my os to Ubuntu 9.04 and I installed the same xampp 1.7.2. Interestingly, when I wanted to run my application under Ubuntu I got an errorMessage: SQLSTATE[HY000] [2002] Invalid argumentAfter googling I found that the reason was that in my php.ini (i.e. for xampp it is /opt/lampp/etc/php.ini) the variable pdo_mysql.default_socket was not set: Therefore I set it to /opt/lampp/var/mysql/mysql.sockOf course, I also had to restart Xamppsudo /opt/lampp/lampp restartIt is interesting why Xampp 1.7.2 worked under Arch Linux, but it did not work under Ubuntu 9.04?