Here's a list of useful things we gain from moving to PHP 5.5 or greater and some info on how it's useful to Traq, and if it's worth it.
PHP 5.5: Not much actually.
- Constant scalar expressions: Because it's nice to have.
- Variadic functions and argument unpacking using the ... operator: No more func_get_args()
- Function and constant importing with the use keyword: Helpers.
Is it worth moving to PHP 5.5? Not until support for 5.4 is close to ending.
Is it worth moving to PHP 5.6? Not for Traq 4.0, definitely worth it later on.