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seanmorris / php-wasm

PHP in Browser, powered by WebAssembly.
https://seanmorris.github.io/php-wasm/
Apache License 2.0
606 stars 32 forks source link
es6 npm php wasm

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seanmorris/php-wasm php-wasm

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PHP in WebAssembly, npm not required.

find php-wasm on npm | github | unpkg | reddit | discord

🌟 v0.0.9-alpha - Aiming for the (GitHub) Stars

changelog

Installing php-wasm:

$ npm i php-wasm@alpha

Installing php-cgi-wasm:

$ npm i php-cgi-wasm@alpha

Installing php-wasm-builder:

$ npm i php-wasm-builder@alpha

☀️ Examples

[React + php-web/php-cgi-worker demo]

Drupal Demo CakePHP Demo CodeIgniter Demo Laravel Demo Laminas Demo Code Editor

🎩 Introducing php-cgi-wasm!

Version 0.0.9 adds php-cgi-wasm to the mix. This allows you to run php in web-server mode, similar to how it runs under apache or nginx. Running within a Service Worker, it can intercept and respond to HTTP requests just like a normal webserver. This means the browser can simply navigate to a URL, and PHP will generate the page, and everything will work as-normal, AJAX and all. From the perspective of the webpage, its just making HTTP requests. Its not worried about whether the PHP runs on the server or in a Service Worker.

Install the php-cgi-wasm package

$ npm install php-cgi-wasm

Example Service Worker:

import { PhpCgiWorker } from "php-cgi-wasm/PhpCgiWorker";

// Spawn the PHP-CGI binary
const php = new PhpCgiWorker({
    prefix:  '/php-wasm',
    docroot: '/persist/www',
    types: {
        jpg:  'image/jpeg',
        jpeg: 'image/jpeg',
        gif:  'image/gif',
        png:  'image/png',
        svg:  'image/svg+xml',
    }
});

// Set up the event handlers
self.addEventListener('install',  event => php.handleInstallEvent(event));
self.addEventListener('activate', event => php.handleActivateEvent(event));
self.addEventListener('fetch',    event => php.handleFetchEvent(event));
self.addEventListener('message',  event => php.handleMessageEvent(event));

You can see examples of php-cgi-wasm running in a service worker and nodejs in demo-web/src/cgi-worker.mjs & demo-node/index.mjs respectively.

Note: php-cgi-wasm & php-wasm are separate packages. One "embeds" php right into your javascript, the other runs in "cgi-mode," just like php would under apache or nginx.

You can find documentation specific to php-cgi-wasm here.

🛠️ Install & Use

Install php-wasm with npm:

$ npm install php-wasm

Include the module in your preferred format:

Common JS

const { PhpWeb } = require('php-wasm/PhpWeb.js');
const php = new PhpWeb;

ESM

import { PhpWeb } from 'php-wasm/PhpWeb.mjs';
const php = new PhpWeb;

From a CDN:

Note: This does not require npm.

jsdelivr
const { PhpWeb } = await import('https://cdn.jsdelivr.net/npm/php-wasm/PhpWeb.mjs');
const php = new PhpWeb;
unpkg
const { PhpWeb } = await import('https://www.unpkg.com/php-wasm/php-wasm/PhpWeb.mjs');
const php = new PhpWeb;

Pre-Packaged Static Assets:

If you're using a bundler, use the vendor's documentation to learn how to move the files matching the following pattern to your public directory:

node_modules/php-wasm/php-web.mjs.wasm
node_modules/php-wasm/php-worker.mjs.wasm # ONLY if you're running the standard build in a worker

For php-cgi-wasm:

node_modules/php-cgi-wasm/php-cgi-worker.mjs.wasm
node_modules/php-cgi-wasm/php-cgi-web.mjs.wasm # ONLY if you're running the cgi build in a page

🍎 Quickstart

Inline PHP

Include the php-tags.js script from a CDN:

<script async type = "text/javascript" src = "https://cdn.jsdelivr.net/npm/php-wasm/php-tags.jsdelivr.mjs"></script>

And run some PHP right in the page!

<script type = "text/php" data-stdout = "#output">
<?php phpinfo();
</script>
<div id = "output"></div>

Inline php can use standard input, output and error with data- attributes. Just set the value of the attribute to a selector that will match that tag.

<script async type = "text/javascript" src = "https://cdn.jsdelivr.net/npm/php-wasm/php-tags.jsdelivr.mjs"></script>

<script id = "input" type = "text/plain">Hello, world!</script>

<script type = "text/php" data-stdin = "#input" data-stdout = "#output" data-stderr = "#error">
    <?php echo file_get_contents('php://stdin');
</script>

<div id = "output"></div>
<div id = "error"></div>

The src attribute can be used on <script type = "text/php"> tags, as well as their input elements. For example:

<html>
    <head>
        <script async type = "text/javascript" src = "https://cdn.jsdelivr.net/npm/php-wasm/php-tags.jsdelivr.mjs"></script>
        <script id = "input" src = "/test-input.json" type = "text/json"></script>
        <script type = "text/php" src = "/test.php" data-stdin = "#input" data-stdout = "#output" data-stderr = "#error"></script>
    </head>
    <body>
        <div id = "output"></div>
        <div id = "error"></div>
    </body>
</html>

CDNs

JSDelivr
<script async type = "text/javascript" src = "https://cdn.jsdelivr.net/npm/php-wasm/php-tags.jsdelivr.mjs"></script>
Unpkg
<script async type = "text/javascript" src = "https://www.unpkg.com/php-wasm/php-tags.unpkg.mjs"></script>

🥤 Running PHP & Taking Output

Create a PHP instance:

const { PhpWeb } = await import('https://cdn.jsdelivr.net/npm/php-wasm/PhpWeb.mjs');
const php = new PhpWeb;

Add your output listeners:

// Listen to STDOUT
php.addEventListener('output', (event) => {
    console.log(event.detail);
});

// Listen to STDERR
php.addEventListener('error', (event) => {
    console.log(event.detail);
});

Provide some input data on STDIN if you need to:

php.inputString('This is a string of data provided on STDIN.');

... then run some PHP!

const exitCode = await php.run('<?php echo "Hello, world!";');

Dynamic Extensions in Static Pages

Dynamic extensions can be loaded in static webpages like so:

<script async type = "module" src = "https://cdn.jsdelivr.net/npm/php-wasm@0.0.9-alpha-12/php-tags.mjs"></script>

<script type = "text/php" data-stdout = "#output" data-stderr = "#error" data-libs = '[
  {"url": "https://unpkg.com/php-wasm-yaml/php8.3-yaml.so", "ini": true},
  {"url": "https://unpkg.com/php-wasm-yaml/libyaml.so", "ini": false}
]'><?php
  print yaml_emit([1,2,3,"string",["k1" => "value", "k2" => "value2", "k3" => "value3"],"now" => date("Y-m-d h:i:s")]);
</script>

⚙️ Configuration

You can pass in the ini property to the constructor to add lines to /php.ini:

const php = new PhpWeb({ini: `
    date.timezone=${Intl.DateTimeFormat().resolvedOptions().timeZone}
    tidy.clean_output=1
    expose_php=0
`});

The /config/php.ini and /preload/php.ini files will also be loaded, if they exist. Neither of these files will be created if they do not exist. They're left completely up to the programmer to create & populate.

Options like the following may appear in these files. See the PHP docs for the full list.

[php]
date.timezone=UTC
tidy.clean_output=1
expose_php=0

CGI Configuration

When running in CGI mode, php will look for a php.ini file in the document root directory, and load it along with the files listed above.

Writing an INI for multiple PHP versions

PHP will replace strings in INI files in the form ${ENVIRONMENT_VARIABLE} with the env value of ENVIRONMENT_VARIABLE. The PHP_VERSION environment variable is available to allow loading of the extension compatible with the currently running version of PHP:

[php]
extension=php${PHP_VERSION}-phar.so

Remember to correctly escape the $ if you're supplying the INI from Javascript with `backtics`:

const php = new PhpWeb({ini: `
    extension=php\${PHP_VERSION}-phar.so
    date.timezone=${Intl.DateTimeFormat().resolvedOptions().timeZone}
`});

🔌 Extensions

Loading extensions at runtime

The following extensions may be loaded at runtime. This allows the shared extension & their dependencies to be cached, re-used, and selected a-la-carte for each application.

There are two ways to load extensions at runtime, using the dl() function or php.ini.

<?php
dl('php-8.3-xml.so');
dl('php-8.3-dom.so');

or, pass an array as the extensions argument to the constructor from Javascript to auto-generate an ini file that loads your extensions:

const php = new PhpWeb({sharedLibs: [
    `php8.3-xml.so`,
    `php8.3-dom.so`,
]});

The class used to load PHP (PhpWeb here) also implements a phpVersion property to ensure libs can be loaded for any compatible version:

const php = new PhpWeb({sharedLibs: [
    `php${PhpWeb.phpVersion}-xml.so`,
    `php${PhpWeb.phpVersion}-dom.so`,
]});

Dynamic Extensions from Remote Servers:

You can also load extensions from remote servers with URLs:

const php = new PhpWeb({sharedLibs: [`https://unpkg.com/php-wasm-phar/php8.3-phar.so`]});

The above is actually shorthand for the following code. Passing ini: true will automatically load the extension via /php.ini, passing ini: false will wait for a call to dl() to do the lookup.

const php = new PhpWeb({sharedLibs: [
    {
        name: `php8.3-phar.so`,
        url:  `https://unpkg.com/php-wasm-phar/php8.3-phar.so`,
        ini:  true,
    }
]});

Strings starting with /, ./, http:// or https:// will be treated as URLs:

const php = new PhpWeb({sharedLibs: [
    `./php8.3-phar.so`
]});

Some extensions require supporting libraries. You can provide URLs for those as sharedLibs as well, just pass ini: false:

(name is implied to be the last section of the URL here.)

const php = new PhpWeb({sharedLibs: [
    { url: 'https://unpkg.com/php-wasm-sqlite/php8.3-sqlite.so', ini: true  },
    { url: 'https://unpkg.com/php-wasm-sqlite/sqlite.so',        ini: false },
]});

Loading Dynamic Extensions as JS Modules:

Dynamic extensions can be loaded as modules: So long as the main file of the module defines the getLibs and getFiles methods, extensions may be loaded like so:

new PhpNode({sharedLibs:[ await import('php-wasm-intl') ]})

Dynamic extensions can also be loaded as modules from any static HTTP server with an ESM directory structure.

// This will load both sqlite.so & php8.x-sqlite.so:
const php = new PhpWeb({sharedLibs: [ await import('https://cdn.jsdelivr.net/npm/php-wasm-sqlite') ]});

Sadly, this notation is not available for Service Workers, since they do not yet support dynamic imports(). Hopefully this will change soon.

Compiling extensions

Extensions may be compiled as dynamic, shared, or static. See Custom Builds for more information on compiling php-wasm.

📦 Loading Files

Loading single files at runtime

When spawning a new instance of PHP, a files array can be provided to be loaded into the filesystem. For example, the php-intl extension requires us to load icudt72l.dat into the /preload directory.

const sharedLibs = [`https://unpkg.com/php-wasm-intl/php\${PHP_VERSION}-intl.so`];

const files = [
    {
        name: 'icudt72l.dat',
        parent: '/preload/',
        url: 'https://unpkg.com/php-wasm-intl/icudt72l.dat'
    }
];

const php = new PhpWeb({sharedLibs, files});

Preloaded FS

Use the PRELOAD_ASSETS key in your .php-wasm-rc file to define a list of files and directories to include by default.

The files and directories will be collected into a single directory. Individual files & directories will appear in the top level, while directories will maintain their internal structure.

These files & directories will be available under /preload in the final package, packaged into the .data file that is built along with the .wasm file.

PRELOAD_ASSETS='/path/to/file.txt /some/directory /path/to/other_file.txt /some/other/directory'

locateFile

You can provide the locateFile option to php-wasm as a callback to map the names of files to URLs where they're loaded from. undefined can be returned as a fallback to default.

You can use this if your static assets are served from a different directory than your javascript.

This applies to .wasm files, shared libraries, single files and preloaded FS packages in .data files.

const php = new PhpWeb({locateFile: filename => `/my/static/path/${filename}`});

💾 Persistent Storage (IDBFS & NodeFS)

IDBFS (Web & Worker)

To use IDBFS in PhpWeb, pass a persist object with a mountPath key.

mountPath will be used as the path to the persistent directory within the PHP environment.

const { PhpWeb } = await import('https://cdn.jsdelivr.net/npm/php-wasm/PhpWeb.mjs');

const php = new PhpWeb({persist: {mountPath: '/persist'}});

NodeFS (NodeJS Only)

To use NodeFS in PhpWeb, pass a persist object with mountPath & localPath keys.

localPath will be used as the path to the HOST directory to expose to PHP. mountPath will be used as the path to the persistent directory within the PHP environment.

const { PhpNode } = await import('https://cdn.jsdelivr.net/npm/php-wasm/PhpNode.mjs');

const php = new PhpNode({persist: {mountPath: '/persist', localPath: '~/your-files'}});

📁 Filesystem Operations

Filesystem Methods

The following EmscriptenFS methods are exposed via the php object:

Note: If you're using php-web in conjunction with php-cgi-worker to work on the filesystem, you'll need to refresh the filesystem in the worker. You can do that with the following call using msg-bus (see below).

// Tell the worker that the FS has been updated
await sendMessage('refresh');

php.analyzePath

Get information about a file or directory.

await php.analyzePath(path);

php.readdir

Get a list of files and folders in or directory.

await php.readdir(path);

php.readFile

Get the content of a file as a Uint8Array by default, or optionally as utf-8.

await php.readFile(path);
await php.readFile(path, {encoding: 'utf8'});

php.stat

Get information about a file or directory.

await php.stat(path);

php.mkdir

Create a directory.

await php.mkdir(path);

php.rmdir

Delete a directory (must be empty).

await php.rmdir(path);

php.unlink

Delete a file.

await php.rmdir(path);

php.rename

Rename a file or directory.

await php.rename(path, newPath);

php.writeFile

Create a new file. Content should be supplied as a Uint8Array, or optionally as a string of text.

await php.writeFile(path, data);
await php.writeFile(path, data, {encoding: 'utf8'});

Transactions

Web and Worker only!

The web and worker build use navigator.locks.request to request a lock named php-wasm-fs-lock before performing filesystem operations. This ensure multiple tabs & the service worker can interact with the filesystem without overwriting eachother's work. Before any FS operation takes place, the entire FS is loaded from IDBFS, and before the lock is released, the entire FS is laoded BACK into IDBFS.

The operations are enqueued asyncronously, so if multiple requests are generated before one transaction closes, they will be batched automatically. This also applies to multiple requests generated before the lock is acquired. There is generally no need to take explicit control of FS mirroring.

To suppress this behavior and take explicit control of the FS mirroring, you can pass the {autoTransaction: false} option to the constructor. Doing this will require you to call php.startTransaction() before any FS operations take place, and thenphp.commitTransaction() when you're done. Using this incorrectly may leave your filesystem in a corrupted state.

php.startTransaction

await php.startTransaction();

php.commitTransaction

await php.commitTransaction();

msg-bus

There is a msg-bus module supplied by php-cgi-wasm as a helper to communicate with php running inside a worker. The module exposes two functions: sendMessageFor and onMessage.

This allows you to simply await the result of calls to file system methods (see above) on the service worker:

const result = await sendMessage(methodName, [param, param, param]);

onMessage & sendMessageFor

import { onMessage, sendMessageFor } from `php-cgi-wasm/msg-bus`;

const SERVICE_WORKER_SCRIPT_URL = '/cgi-worker.mjs';

navigator.serviceWorker.register(SERVICE_WORKER_SCRIPT_URL);

navigator.serviceWorker.addEventListener('message', onMessage);

const sendMessage = sendMessageFor(SERVICE_WORKER_SCRIPT_URL);

const result = await sendMessage(methodName, [param, param, param]);

php.handleMessageEvent

Once you've got the above set up, use php.handleMessageEvent to handle the message events on the service worker:

self.addEventListener('message',  event => php.handleMessageEvent(event));

🏗️ Custom Builds

To use the the in-place builder, first install php-wasm-builder globally:

Requires docker, docker-compose, coreutils, wget, & make.

$ npm install -g php-wasm-builder

Create the build environment (can be run from anywhere):

$ php-wasm-builder image

Optionally clean up files from a previous build:

$ php-wasm-builder clean

Build for web

Then navigate to the directory you want the files to be built in, and run php-wasm-builder build

$ cd ~/my-project
$ php-wasm-builder build
# php-wasm-builder build web
#  "web" is the default here

Build for node

$ cd ~/my-project
$ php-wasm-builder build node

ESM Modules:

Build ESM modules with:

$ php-wasm-builder build web mjs
$ php-wasm-builder build node mjs

CGI Modules:

Build CGI modules with:

$ php-wasm-builder build web cgi mjs
$ php-wasm-builder build worker cgi mjs

This will build the package inside of the current directory (or in PHP_DIST_DIR, see below for more info.)

.php-wasm-rc

You can also create a .php-wasm-rc file in this directory to customize the build.

# Select a PHP version
PHP_VERSION=8.3

# Build the package to a directory other than the current one (RELATIVE path)
PHP_DIST_DIR=./public

# Build the extensions to a directory other than the current one (RELATIVE path)
PHP_ASSET_DIR=./public

# Build the cgi package to a directory other than the current one (RELATIVE path)
PHP_CGI_DIST_DIR=./public

# Build the cgi package's extensions to a directory other than the current one (RELATIVE path)
PHP_CGI_ASSET_DIR=./public

# Space separated list of files/directories (ABSOLUTE paths)
# to be included under the /preload directory in the final build.
PRELOAD_ASSETS=~/my-project/php-scripts ~/other-dir/example.php

# Memory to start the instance with, before growth
INITIAL_MEMORY=2048MB

# Build with assertions enabled
ASSERTIONS=0

# Select the optimization level
OPTIMIZATION=3

# Build with extensions
WITH_GD=1
WITH_LIBPNG=1
WITH_LIBJPEG=1
WITH_FREETYPE=1

Options

The following options may appear in .php-wasm-rc.

PHP_VERSION

8.0|8.1|8.2|8.3

PHP_DIST_DIR

This is the directory where javascript & wasm files will be built to, relative to the current directory.

PHP_ASSET_DIR

This is the directory where shared libs, extension, .data files & other supporting files will be built to, relative to the current directory. Defaults to PHP_DIST_DIR.

OPTIMIZE

0|1|2|3

The optimization level to use while compiling.

SUBOPTIMIZE

The optimization level to use while compiling libraries. Defaults to OPTIMIZE.

PRELOAD_ASSETS

A list of absolute paths to files & directories to build to the /preload directory. Will produce a .data file.

ASSERTIONS

0|1

Build with/without assertions.

Extensions

As stated above, extensions may be compiled as dynamic, shared, or static.

(defaults provided below in bold)

The following options are availavle for building static PHP extensions:

WITH_BCMATH    # [0, 1] Enabled by default
WITH_CALENDAR  # [0, 1] Enabled by default
WITH_CTYPE     # [0, 1] Enabled by default
WITH_EXIF      # [0, 1] Enabled by default
WITH_FILTER    # [0, 1] Enabled by default
WITH_TOKENIZER # [0, 1] Enabled by default
WITH_VRZNO     # [0, 1] Enabled by default

The following extension may be compiled as static, shared or dynamic:

WITH_PHAR      # [0, 1, static, dynamic]
WITH_LIBXML    # [0, 1, static, shared]
WITH_LIBZIP    # [0, 1, static, shared, dynamic]
WITH_ICONV     # [0, 1, static, shared, dynamic]
WITH_SQLITE    # [0, 1, static, shared, dynamic]

WITH_GD        # [0, 1, static, shared, dynamic]
WITH_ZLIB      # [0, 1, static, shared, dynamic]
WITH_LIBPNG    # [0, 1, static, shared]
WITH_FREETYPE  # [0, 1, static, shared]
WITH_LIBJPEG   # [0, 1, static, shared]

WITH_YAML      # [0, 1, static, shared, dynamic]
WITH_TIDY      # [0, 1, static, shared, dynamic]
WITH_MBSTRING  # [0, 1, static, dynamic]
WITH_ONIGURUMA # [0, 1, static, shared]
WITH_OPENSSL   # [0, 1, shared, dynamic]
WITH_INTL      # [0, 1, static, shared, dynamic]
WITH_PHAR

static|dynamic

When compiled as a dynamic extension, this will produce the extension file php8.x-phar.so.

WITH_LIBXML

static|shared

This actual php-libxml extension must be statically compiled, but libxml itself may be loaded as a shared library.

When compiled as a shared library, it will produce the library libxml.so.

WITH_LIBZIP

static|shared|dynamic

When compiled as a dynamic extension, this will produce the extension php-8.x-zip.so.

When compiled as a dynamic or shared extension, it will produce the library libzip.so.

This extension depends on zlib.

WITH_ICONV

static|shared|dynamic

When compiled as a dynamic extension, this will produce the extension php-8.x-iconv.so.

When compiled as a dynamic or shared extension, it will produce the library libiconv.so.

WITH_SQLITE

static|shared|dynamic

When compiled as a dynamic extension, this will produce the extensions php-8.x-sqlite.so, & php-8.x-pdo-sqlite.so.

When compiled as a dynamic or shared extension, it will produce the library libsqlite3.so.

WITH_GD

static|dynamic

This extenstion makes use of freetype, libjpeg, libpng, & zlib.

When compiled as a dynamic extension, this will produce the extension php-8.x-gd.so.

WITH_LIBPNG

static|shared

When compiled as a shared library, this will produce the library libpng.so.

If WITH_GD is dynamic, then loading will be deferred until after gd is loaded.

WITH_FREETYPE

static|shared

When compiled as a shared library, this will produce the library libfreetype.so.

If WITH_GD is dynamic, then loading will be deferred until after gd is loaded.

WITH_LIBJPEG

static|shared

When compiled as a shared library, this will produce the library libjpeg.so.

If WITH_GD is dynamic, then loading will be deferred until after gd is loaded.

WITH_ZLIB

static|shared|dynamic

When compiled as a dynamic extension, this will produce the extension php-8.x-zlib.so.

When compiled as a dynamic or shared extension, it will produce the library libz.so.

WITH_YAML

static|shared|dynamic

When compiled as a dynamic extension, this will produce the extension php-8.x-yaml.so.

When compiled as a dynamic or shared extension, it will produce the library libyaml.so.

WITH_TIDY

static|shared|dynamic

When compiled as a dynamic extension, this will produce the extension php-8.x-tidy.so.

When compiled as a dynamic or shared extension, it will produce the library libtidy.so.

WITH_MBSTRING

static|dynamic

When compiled as a dynamic extension, this will produce the extension php-8.x-mbstring.so.

WITH_ONIGURUMA

static|shared|dynamic

Support library for mbstring.

When compiled as a dynamic or shared library, this will produce the library libonig.so.

If WITH_MBSTRING is dynamic, then loading will be deferred until after mbstring is loaded.

WITH_OPENSSL

shared|dynamic

When compiled as a dynamic extension, this will produce the extension php-8.x-openssl.

When compiled as a dynamic or shared extension, it will produce the libraries libssl.so & libcrypto.so.

WITH_INTL

static|shared|dynamic

When compiled as a dynamic, or shared extension, this will produce the extension php-8.x-intl.so & the following libraries:

php-wasm-builder commands

php-wasm-builder build

Use this to build custom version of php-wasm. Its recommended to build this to an empty directory using a .php-wasm-rc file.

npx php-wasm-builder build

php-wasm-builder image

This will build the docker container used to build php-wasm.

npx php-wasm-builder image

php-wasm-builder copy-assets

This will scan the current package's node_modules directory for shared libraries & supporting files, and copy them to PHP_ASSET_DIR.

You can use this with .php-wasm-rc to copy assets even if you're not using a custom build.

npx php-wasm-builder copy-assets

php-wasm-builder build-assets

Similar to copy-assets, but will actually compile the shared libaries, then copy them to PHP_ASSET_DIR.

You can use this with .php-wasm-rc to copy assets even if you're not using a custom build.

npx php-wasm-builder build-assets

php-wasm-builder clean

Clear cached build resources.

npx php-wasm-builder clean

php-wasm-builder deep-clean

Clear out all downloaded dependencies and start from scratch.

npx php-wasm-builder deep-clean

php-wasm-builder help

Print the help text for a given command

npx php-wasm-builder help COMMAND

🤝 php-wasm started as a fork of oraoto/PIB...

The repository pib-legacy was created to preserve the original state of the project.

https://github.com/oraoto/pib

The repository pib-legacy was created to preserve the original state of the project: https://github.com/seanmorris/pib-legacy

🍻 Licensed under the Apache License, Version 2.0

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

http://www.apache.org/licenses/LICENSE-2.0

Special thanks to Alex Haussmann