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Message-ID: <DC8C0F88-1B43-4601-A3D1-2EEA812B89B9@newclarity.net>
Date: Sat, 26 Oct 2019 22:12:35 -0400
Cc: Benjamin Morel <benjamin.morel@gmail.com>,
 Dmitry Stogov <dmitry@zend.com>
To: PHP internals <internals@lists.php.net>
Subject: Optional pre-compiler for PHP8?
From: mike@newclarity.net (Mike Schinkel)

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Hello all:

While reading the [RFC] Union Types v2 thread and comments from =
Dmitry[1], and especially Benjamin[2] who suggested "building a static =
analysis tool which could prove that certain type checks would never =
fail, and prime OpCache" it occurred to me that a PHP pre-compiler could =
potentially be used to resolve numerous issues the community has been =
debating.

But first, let me define what I envision for a pre-compiler:=20

- A command-line tool that could take a PHP file and/or application and =
generate pre-compiled files with an extension of .phpc or similar.
- This of these .phpc files being implemented similar to .phar` files, =
but actually compiled to a OpCache binary form.
- Pre-compiled files would be deployed alongside .php files, or =
optionally(?) standalone without PHP files.
- Libraries and (WordPress) plugins could deliver pre-compiled files =
too, alongside their .php source files

- Command line switches could allow for:
- Compiling with or without (selected) deprecations
- Selected constants defined on the command line
- Packaging code on a one-to-one per PHP file, as one file per =
namespace, one file per app, etc.

- The pre-compilation process would be able to:
- Type-check everything that has type-hints
- Do type checking that is too expensive to do at runtime

- Pre-compiling:=20
- Could help eliminate the complexity of auto-loading and opening many =
files, at least for pre-compiled code.
- Would be an option for type checking and improved performance, but not =
be required.

If the PHP community were to embrace the idea of an optional =
pre-compiler then we could see the following benefits:

1. Full type checking capability without any concerns for runtime =
performance issues related to type checking.

2. Ability to significant improve performance over time, possibly even =
more than a JIT model.

3. Potential to support optimized real types =E2=80=94 as in Hack =E2=80=94=
 where code needs to be highly performant=20

4. Ability to deprecate features for pre-compiled code while still =
supporting them when not precompiled.

While benefits #1 to #3 are highly valuable, consider benefit #4. If we =
had such a pre-compiler than the concern for BC for pre-compiled code =
could become moot as the deprecations would not affect any existing code =
that is not pre-compiled. =20

This could potentially give us the best of both worlds?

Further, those most interested in deprecations and moving to enterprisey =
language features certainly use a CI/CD build process so it should be =
not problem at all for them to incorporate a pre-compile step.

Lastly, having such an optional process =E2=80=94 with its primary =
promoted benefit being performance =E2=80=94 could be a great incentive =
for those running less strict and backwards-compatible PHP code to =
refactor their source code to gain greater performance.  This contrasts =
with deprecating features and breaking BC just "because it is a better =
way to program." Give them a carrot rather than use a stick.

So for those who know PHP's internal core code:=20

Is there any reason this is not technically viable?

And for everyone:=20

What do you think of this as a potential future for PHP?

-Mike

[1] https://news-web.php.net/php.internals/107699
[2] https://news-web.php.net/php.internals/107702=

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