It took a while for XenForo to add limited support for php 5.4. I say limited as there are still some areas where this needs improving. I'm placing my request now, that the XenForo Development Team follow and track the development of php 5.5 when time allows. php 5.5 Alpha 1 has been released and no, I do not expect anyone to support it at this time in its Alpha or Beta state. Only that it not be delayed and that upon its gold release, that it be included in future versions of XenForo. I would suggest also dropping support for php 5.2 which is almost 3 years old, past discontinued and end of life.