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Subject: Re: [PHP-DEV] PHP build for the wasm32-wasi target
From: george.banyard@gmail.com ("G. P. B.")

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On Thu, 22 Dec 2022 at 16:04, Rafael Fern=C3=A1ndez L=C3=B3pez <rfernandezl=
@vmware.com>
wrote:

> Hello community,
>
> I am reaching out on behalf of the WasmLabs team at the Office of the CTO
> at VMware.
>
> We have been working on building PHP for WebAssembly, specifically for th=
e
> wasm32-wasi target. WASI [1] is a system interface that allows WebAssembl=
y
> to run on the server side by safely being able to access operating
> system-like features, including files and filesystems, Berkeley sockets,
> clocks and random numbers [2].
>
> WebAssembly in the server side is experiencing a big growth both in
> interest and users. There are other programming language interpreters tha=
t
> can be compiled to wasm32-wasi as of today; for example: Python [3] and
> Ruby [4].
>
> We have patches for PHP 7.3.33 and 7.4.32 at the time of writing. Porting
> PHP 8.2.0 is work in progress at this time.
>
> In the interest of getting feedback from the PHP community I am providing
> links to the patches at GitHub. Please, let us know what would be the nex=
t
> step to contribute and continue to maintain this work upstream. We look
> forward to work with the PHP community.
>
> If you want to try it out, you can download the binaries we are producing
> in the CI/CD pipeline for 7.3.33 [5] and 7.4.32 [6]. You can use a
> WASI-enabled WebAssembly runtime such as Wasmtime [7] to run PHP compiled
> to wasm32-wasi.
>
> Patches: 7.3.33 [8], 7.4.32 [9][10].
>
> Example execution:
>
> ```
> $ wasmtime -- --dir ~/php-example php-cgi-7.4.32.wasm
> ~/php-example/hello/index.php
> X-Powered-By: PHP/7.4.32
> Content-type: text/html; charset=3DUTF-8
>
> Hello, world!
> ```
>
> We have already presented some of this work at OSS conferences and events
> like Kubecon and Docker Community days, and have written a few articles
> providing the background to the port, its limitations and what can
> currently be accomplished (including running WordPress!). Please find bel=
ow
> some links to the talks and articles:
>
> - Porting PHP to WebAssembly using WASI  [11]
> - Running WordPress with WebAssembly using mod_wasm and Apache  [12]
> - WebAssembly: Docker without containers! [13]
> - mod_wasm: Bringing WebAssembly to Apache [14]: this talk builds on top
> of PHP 7.3.33 and shows WordPress running with sqlite on top of Apache,
> thanks to an Apache module (mod_wasm) that is able to execute WebAssembly
> modules.
> - Docker and WebAssembly, better together [15]: this presentation feature=
s
> PHP 7.4.32 and explains a bit of the context of this work.
>
>
> Thank you,
> Rafael Fern=C3=A1ndez L=C3=B3pez.
>
> [1] https://wasi.dev/
> [2]
> https://github.com/bytecodealliance/wasmtime/blob/03463458e426d4bd0601ebd=
82e95b668fc982443/docs/WASI-intro.md
> [3] https://docs.python.org/3/whatsnew/3.11.html
> [4] https://www.ruby-lang.org/en/news/2022/12/06/ruby-3-2-0-rc1-released/
> [5]
> https://github.com/vmware-labs/webassembly-language-runtimes/releases/tag=
/php%2F7.3.33%2B20221124-2159d1c
> [6]
> https://github.com/vmware-labs/webassembly-language-runtimes/releases/tag=
/php%2F7.4.32%2B20221124-2159d1c
> [7] https://wasmtime.dev/
> [8]
> https://github.com/vmware-labs/webassembly-language-runtimes/tree/main/ph=
p/php-7.3.33/patches
> [9]
> https://github.com/vmware-labs/webassembly-language-runtimes/blob/main/ph=
p/php-7.4.32/patches/0001-Initial-port-of-7.3.33-patch-to-7.4.32.patch
> [10]
> https://github.com/vmware-labs/webassembly-language-runtimes/blob/main/ph=
p/php-7.4.32/patches/0002-Fix-mmap-issues.-Add-readme.patch
> [11] https://wasmlabs.dev/articles/php-wasm32-wasi-port/
> [12] https://wasmlabs.dev/articles/running-wordpress-with-mod-wasm/
> [13] https://wasmlabs.dev/articles/docker-without-containers/
> [14] https://www.youtube.com/watch?v=3DjXe8kulUscQ
> [15] https://youtu.be/yo30oF1Gflo?t=3D7361


Hello Rafael,

While this is impressive, this looks very similar to
https://github.com/seanmorris/php-wasm in that it compiles the whole
interpreter to WASM.
Something I personally find of rather limited utility, even more so when in
this iteration when the current interpreter already works server side.
Mainly because I don't really see what benefits this gives to the language.
Wouldn't this be just slower than executing the interpreter currently?

I spent some time a couple of months ago thinking about trying to actually
compile PHP code to WASM directly *without* compiling the whole
interpreter, be that either by only compiling the existing opcodes to WASM
or compiling directly from PHP to WASM. Now, this is clearly several
magnitudes harder as a problem to solved, but is one that seems to have
more benefits than just compiling the interpreter.
Having a lot of the standard library, actually written in PHP, would be a
big benefit here. And would make this project similar to RPython (what PyPy
uses to compile its Python subset into C).

The other issue is that I don't know of a way to run WASM binaries from PHP
at the moment, from a quick search and from what I remembered Tuleap [1]
achieved this by executing the WASM via Rust and using FFI to call the Rust
function from PHP, which looks extremely clunky and something that maybe
should be improved as an orthogonal project.

Best regards.

George P. Banyard

[1]
https://blog.tuleap.org/untrusted-code-execution-in-php-with-ffi-and-webass=
embly

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