# Yet Another Stupid Question: Why Bother with Compatibility? - Thread: https://externals.io/message/15974 - Original archive: https://news-web.php.net/php.internals/15974 - Started by GamblerZG on 2005-04-15T17:03:44+00:00 - Messages: 3 - Reply by email to internals@lists.php.net - More for agents: search with https://externals.io/search.md?q={query} · JSON API at https://externals.io/api · documentation at https://externals.io/llms.txt --- ## #15974 — GamblerZG — 2005-04-15T17:03:44+00:00 URL: https://externals.io/message/15974#15974 Maintaining compatibility between different major versions of PHP must be extremely hard. Maybe that is obvious, but I do not quite understand why developers do it. Why PHP 5 has to understand deprecated syntax of PHP 4? I mean, if someone needs to execute old scripts, they can always use old engine. --- ## #15976 — Paul Reinheimer — 2005-04-15T17:49:15+00:00 URL: https://externals.io/message/15974#15976 · In reply to: #15974 The advantage of maintaining reverse compatibility is that it helps encourage people to upgrade. Many more people would have many more concerns if the 4 -> 5 upgrade broke programs using depreciated practices. ISPs and hosting companies in particular would be extremely reluctant to upgrade as it would promptly result in several (hundred?) support tickets asking "My code worked yesterday, now it doesn't! What did you do?!!!!!?!!". I will be honest, I've written the majority of my code in the last year, but am I 100% positive that I'm not using anything that was marked as depreciated in PHP 4? Absolutely not. For all I know I might be using some deprecated function in some arcane, rarely used administrative include file hiding somewhere in the depths of my file system. Everything would apparently keep working when I upgraded, and even for days/weeks after the fact. Then boom, one day something important brakes, and I have no idea why. I would assume that the percentage of people willing to upgrade is directly proportional to the percentage of BC. just my 2cents (canadian). paul > Maintaining compatibility between different major versions of PHP must > be extremely hard. Maybe that is obvious, but I do not quite understand > why developers do it. Why PHP 5 has to understand deprecated syntax of > PHP 4? I mean, if someone needs to execute old scripts, they can always > use old engine. > > -- > > > > -- Paul Reinheimer Zend Certified Engineer --- ## #15977 — GamblerZG — 2005-04-15T19:07:53+00:00 URL: https://externals.io/message/15974#15977 · In reply to: #15976 Paul Reinheimer wrote: > The advantage of maintaining reverse compatibility is that it helps encourage > people to upgrade. Many more people would have many more concerns if the > 4 -> 5 upgrade broke programs using depreciated practices. Well, that's the thing I don't get. If I have working system for PHP 4 engine, why would I want to _upgrade_ (i.e. switch) to PHP 5 engine? Would it not be more compelling for me to have 4 and 5 as separate Apache modules or something like that? Interoperability problem could be solved by some kind of inter-version bridge (like PHP/Java integration module). A the same time, this would free PHP developers from BC. > I will be honest, I've written the majority of my code in the last > year, but am I > 100% positive that I'm not using anything that was marked as depreciated in > PHP 4? Absolutely not. For all I know I might be using some deprecated function > in some arcane, rarely used administrative include file hiding somewhere in the > depths of my file system. Everything would apparently keep working when I > upgraded, and even for days/weeks after the fact. Then boom, one day something > important brakes, and I have no idea why. Look at your situation from different perspective. Wouldn't it be nice to be absolutely sure that your website does not uses any deprecated code? You would most certainly know that if PHP 3 and PHP 4 would be handled by different engines.