I've serious problems for installing new versions of XAMPP (for Linux) that come with PHP 5.3 (such as 1.7.2 and 1.7.3a). I've tested that on Karmic Koala Ubuntu.
The message obtained after add extension xmlrpc.so (coming in php5-xmlrpc's debian package) and restart lamp is:
" undefined symbol: second_arg_force_ref in Unknown on line 0 ".
I've followed these instructions to add support for XMLRPC: viewtopic.php?f=17&t=34264
Finally, i've got back to a version of XAMPP based on PHP 5.2, exactly XAMPP 1.6.7, since I haven't knew how to solve it!
Anyone knows a solution? This issue is important for next generation of XAMPP.