Hi Stephen,
Le 13/11/2015 22:35, Stephen Coakley a écrit :
Hello all,
I've been thinking about PHP optimization and distribution, and I
would like to hear some opinions on introducing a new feature for a
future PHP 7 version. Here's the concept: allow PHP opcode to be both
saved after parsing a file, and to be loaded and executed, similar to
the bcompiler extension and the APC bin functions back in the day.
The advantages are clear: libraries and applications could be compiled
to opcode ahead of time so PHP wouldn't have to compile it again and
again (assuming you're not already using OPcache).
A new function could be provided to parse a PHP file, but instead of
executing it, the compiled opcode would be saved to a file. It might
part of the OPcache extension if it makes sense, and could be called
opcache_compile_to_file() or something.
Another option would be to add a command-line flag to the interpreter
to write compiled opcode instead of executing it after parsing.
Another part of the feature would be to enable the interpreter to
execute compiled opcode scripts directly. This would work for both
compiled scripts passed to the interpreter, and scripts loaded with
`include` and `require`. We would probably need to introduce a new
file extension to specify opcode files. I'd recommend *.phpo or *.phpc.
This is quite similar to Python's ability to execute Python scripts
compiled to bytecode as *.pyc files. The feature has seen great
success in Python, mostly for distributing releases of software or
deploying to a server.
I'm not at this moment planning an RFC, but I'd like to gauge your
opinions and reactions first.
AFAIK, generated bytecodes are not compatible across PHP versions. It
may work for relatively similar versions and preferably in acscending
order (executor more recent than compiler) but nothing is guaranteed.
So, in practice, you cannot distribute pre-compiled code if you must
impose a specific PHP version to execute it.
Python chose to maintain a backwards compatibility between compiler and
executor. PHP chose to cache transient opcodes. It may seem weaker but,
IMO, this is a better approach because it allows a total freedom when
creating, deprecating, and managing opcodes. Working on the engine would
be much harder if we had to maintain BC on pre-compiled code.
In practice, distributing pre-compiled PHP scripts wouldn't have any
noticeable impact on performance because anyone whi cares about
performance will enable opcache first (which should even be enabled by
default, IMO). As Sara noticed, the only benefit would be obfuscation,
which probably deserves a more powerful and reliable mechanism.
Regards
François
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