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Date: Mon, 13 Jan 2020 14:26:32 -0500
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To: Larry Garfield <larry@garfieldtech.com>
Subject: Re: [PHP-DEV] Introducing compile time code execution to PHP
 preloading
From: mike@newclarity.net (Mike Schinkel)

> On Jan 13, 2020, at 1:31 PM, Larry Garfield <larry@garfieldtech.com> =
wrote:
>=20
> On Sun, Jan 12, 2020, at 6:45 PM, Mike Schinkel wrote:
>>> On Jan 12, 2020, at 1:57 PM, Larry Garfield <larry@garfieldtech.com> =
wrote:
>>>=20
>>> Most notably, *not all code will be run in a preload context*. =20
>>=20
>> Can you give some concrete examples here?
>>=20
>>> Language features that only sometimes work scare me greatly. =20
>>=20
>> Do you have some examples of  language features, from PHP or another=20=

>> language, that only work sometimes and that are known to be=20
>> problematic. and why they are problematic?
>=20
> To use the example from the OP:
> <snip>
> I can see the use of that, sure.  Now, what happens when the code is =
not preloaded?  Does that block not get run, and thus CONST_ARRAY is not =
defined?  Does it run on all requests if not preloaded?  How does that =
interact with a file that gets read multiple times?
> <snip>

Thanks so much for going into such detail.  It really helped me =
understand your concerns.

I have been planned to propose an alternate to `static_run` because it =
did not seem to me to be an ideal solution.  And my proposal would not =
have included modifying the AST per se, even though I think that could =
be beneficial. Instead it would just be focused on userland preloading =
(vs. system admin preloading.)
IOW a preload feature that does not require restarting FPM but could =
instead be controlled by the userland developer.

But before I introduce that I want to better understand why you think =
having things that can only run during preload and having things that =
can only run during runtime would be a bad thing.  To me it seems like a =
benefit.  Preload vs. runtime are two different contexts.  Having =
different behavior for different contexts only makes sense IMO.  Look at =
CLI vs. FPM contexts:

- https://stackoverflow.com/a/25653068/102699

I get your concern about recursion, but if that kind of issue is really =
a concern I don't see why we could not artificially limit recursion on =
preload to a configurable amount, with 100 being the default?

Again, if we can I hope we can focus on concrete problems this would =
cause that we might be able to solve vs limiting to only abstract =
concerns.

--------------

Separately I think it would make sense to provide a set of APIs to do =
the most commonly needed things that people might want to modify the AST =
for.

One example that I could envision that would make sense for preload but =
probably not for runtime is an extension of the Reflection API that =
would allow code to define classes, interfaces, traits, functions, etc. =
Here is something I mocked up that I called "Projection" to illustrate =
that concept:

- https://gist.github.com/mikeschinkel/e07eb14a34ce83a96198744e18b0c961

--------------

I do completely see your points about the AST and most PHP developers. =20=


The unfortunate problem with PHP is there is no way to use 3rd party =
code to extend PHP w/o being able to reconfigure the server by adding =
extensions. It would be nice if we could come up with a way for 3rd =
party developers writing in C or another language =E2=80=94 people who =
are more likely to test their code before distributing it =E2=80=94 to =
extend PHP such as by generating OpCode files that a userland developer =
could load. =20

Or maybe we implement ability to load Web Assembly on the server?  If =
that were possible I could write PHP extensions in Go. :-)

I think these discussions should be on a different thread though. I =
think we have 3 different topics here:

- Userland preloading
- Projection API and related
- Userland loadable extensions

-Mike