We plan to raise the min. required PHP version for the ISPConfig UI and server part from PHP 5.2 to PHP 5.3 with the ISPConfig 3.1 release. This allows us to clean up the code and remove workarounds for PHP 5.2. PHP 5.3 is available for the still supported Centos 6 and Ubunru LTS versions, so I don't see any problem here to raise the min. version. If you have any comments on why we can't raise the PHP min version to 5.3, then please let me know.