The PHP extension to run WebAssembly
The goal of the project is to be able to run WebAssembly binaries from
PHP directly. So much fun coming!
What is WebAssembly?
Quoting the WebAssembly site:
WebAssembly (abbreviated Wasm) is a binary instruction format for a
stack-based virtual machine. Wasm is designed as a portable target
for compilation of high-level languages like C/C++/Rust, enabling
deployment on the web for client and server applications.
About speed:
WebAssembly aims to execute at native speed by taking advantage of
common hardware
capabilities
available on a wide range of platforms.
About safety:
WebAssembly describes a memory-safe, sandboxed execution
environment […].
Goals
This extension has some goals in minds. Let's list some of them:
Write PHP extensions
Taking the example of an image manipulation library, like face
detection, one can use an existing Rust or C++ library, then compile
it to a WebAssembly binary, and use it directly in PHP through the
php-ext-wasm extension.
Writing a C extension for PHP with the Zend API is no longer necessary.
Cross-platform distribution and packaging (feat. Composer)
Because WebAssembly is a portable target, i.e. binaries are platform
agnostics, once a library has been compiled to a WebAssembly binary,
it is immediately distributable on all platforms where PHP runs. There
is no compilation steps required. And to be clear, compiling a library
to a WebAssembly binary does not required any PHP headers.
To push the logic further, a library compiled as a WebAssembly binary
can be packaged with Composer (the PHP
dependency manager), along with some PHP code to ease the manipulation
of the compiled library.
Distributing a new version of a WebAssembly binary simply reduces to
distributing a new file. Composer can also add constraints over the
available extensions with their
versions (see
ext-name). All packaging scenarios are handled.
As fast as possible
We are working on being as fast as native code (see [this blog post to
learn more][wasmi-to-wasmer]). So far, the extension provides a faster
execution than PHP itself. With the nbody benchmark, the
php-ext-wasm is 9.5 times faster than pure PHP:, subject, mean, mode, best, rstdev, --, -:, -:, -:, -:, wasm_extension, 2,009.335μs, 1,991.778μs, 1,968.595μs, 2.17%, pure_php, 19,714.738μs, 19,143.083μs, 18,853.399μs, 3.58%, [wasmi-to-wasmer]: https://medium.com/wasmer/php-ext-wasm-migrating-from-wasmi-to-wasmer-4d1014f41c88
Safety first
WebAssembly brings safety guarantees, notably due to its memory model
and its sandboxed execution
environment. If
Rust is used as the source of a WebAssembly binary, then more safety
is brought in the game. In any case, without real numbers or studies,
we imagine that it is safer to use a WebAssembly binary extension
rather than writing C code.
A WebAssembly binary has no access to the PHP environment (so no
access to its memory or functions). It is executed in a sandbox. A
WebAssembly binary is totally blind regarding the host/the system
where it runs: Whether it runs in a Web browser, a server, or a PHP
process, this is the same.
Example
There is a toy program in examples/simple.rs, written in Rust
(or any other language that compiles to Wasm):
#[no_mangle]
pub extern fn sum(x: i32, y: i32) -> i32 {
x + y
}
This program compiles to Wasm, with just compile-wasm examples/simple. We end up with a examples/simple.wasm binary file.
Then, we can execute it in PHP (!) with the examples/simple.php file:
$instance = new Wasm\Instance(__DIR__ . '/simple.wasm');
var_dump(
$instance->sum(5, 37) // 42!
);
And then, finally, enjoy by running:
$ php -d extension=wasm examples/simple.php
int(42)
Usage
This repository contains basically two things:
- The
php-ext-wasmextension, and - The
Wasmlibrary.
The php-ext-wasm extension provides a raw API around
WebAssembly. The Wasm library is a layer on top of php-ext-wasm to
provide more safety and a more user-friendly API.
See the API documentations with examples.
To compile the entire project, run the following commands:
$ just build
$ php -d extension=wasm examples/simple.php
If the provided shared libraries are not compatible with your system,
please try running just build-runtime first.
(Yes, you need just).
Testing
Once the extension is compiled and installed (just run just rust && just php), run the following commands:
$ composer install
$ composer test
License
The entire project is under the MIT License. Please read the
LICENSE
file.