On 08/02/2015 12:30, Lester Caine wrote:
Currently it is impossible to run the PHP5.2 code base on PHP5.4. That is a simple fact. So I can't do between 5.2 and 5.4 what I am currently doing between 5.4 and 7. The code has to be reworked ... so what ever anybody says PHP5 .4*IS* PHP6 in terms of major breaks.
We have a single code base happily running on 5.2, 5.3, 5.4, and I think even 5.5, so it is definitely possible with some code bases. There were a few pieces that had to be changed to work right under 5.3 and 5.4, but none for which the new solution didn't also work under 5.2 (or, at least, for which a compromise didn't exist which worked under both). Call-time pass-by-reference was all over the place, for instance, but rarely actually needed, and if it was, replacing it with a pass-by-reference declaration would leave you with something working fine under 5.2.
It's frustrating not being able to use new features when you need to support an outdated installation, and finding third-party libraries which support old versions of PHP can be tricky. 5.3 was the big breaking point there, because although we didn't refactor our code to use namespaces, libraries quickly came to be written with them (which is a good thing) so automatically have that as a minimum version requirement.
The biggest problem with keeping userland code cross-version compatible is usually syntax - behaviours and standard functions can, if it's really necessary, be worked around by checking PHP_VERSION, or "if ( ! function_exists('blah') { function blah { ... } }". But because there's no equivalent of a C pre-processor, you can't work around syntax which wasn't valid on older versions, other than by not using it (it would have been lovely to include closures in code which was simply unreachable on 5.2 hosts, but if 5.2 needed to parse that file, it was impossible).
Clearly, your experience is different; perhaps some specific examples of the problems which forced you to fork the codebase, rather than adapt it into a cross-compatible state, would help people look out for the same situation arising in future.
Regards, -- Rowan Collins [IMSoP] -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
