🥒 Phikl - Apple's Pkl Bridge for PHP

Phikl (pronounced "fickle") is a PHP binding for Apple's PKL language. This library uses the official PKL CLI tool from Apple and provides a PHP interface to it.

Installation

You can install this library using composer:

composer require alexandre-daubois/phikl

The CLI tool must be installed on your system. You can either install it manually and set the PKL_CLI_BIN environment variable to the path of the binary or use the install subcommand of the pkl command to download the latest supported version of the PKL CLI tool into the vendor/bin directory.

vendor/bin/phikl install

You can also set the download location by using the --location option:

vendor/bin/phikl install --location=/usr/local/bin

If you do so, you must set the PKL_CLI_BIN environment variable to the path of the binary.

Usage

⚠️ If you plan to use this tool in production, it is highly recommended to cache the PKL modules.

Using the CLI tool

This package offers a CLI tool to interact with the PKL CLI tool. You can use the phikl command to interact with the PKL CLI tool, among other things.

Here are some examples of how to use the phikl command:

# Install the PKL CLI tool
vendor/bin/phikl install

# Update/Force install the last supported PKL CLI tool
vendor/bin/phikl update

# Print current PKL CLI tool version
vendor/bin/phikl version

# Evaluate one or many PKL file
vendor/bin/phikl eval config/simple.pkl config/nested.pkl

Using Pkl in PHP

The main way to use this library is to evaluate PKL code. You can do this by using the evaluate method of the Pkl class.

Basic Usage with PklModule

Let's say you have the following PKL code:

/// config/simple.pkl

name = "Pkl: Configure your Systems in New Ways"
attendants = 100
isInteractive = true
amountLearned = 13.37

You can evaluate this code like this:

use Phikl\Pkl;

$module = Pkl::eval('config/simple.pkl');

// you can then interact with the module
echo $module->get('name'); // Pkl: Configure your Systems in New Ways
echo $module->get('attendants'); // 100
echo $module->get('isInteractive'); // true
echo $module->get('amountLearned'); // 13.37

This also works with nested modules:

/// config/nested.pkl

woodPigeon {
    name = "Common wood pigeon"
    diet = "Seeds"
    taxonomy {
        species = "Columba palumbus"
    }
}

use Phikl\Pkl;

$module = Pkl::eval('config/nested.pkl');

// you can then interact with the module
echo $module->get('woodPigeon')->get('name'); // Common wood pigeon
echo $module->get('woodPigeon')->get('diet'); // Seeds
echo $module->get('woodPigeon')->get('taxonomy')->get('species'); // Columba palumbus

Cast to other types

You can cast the values to other types using the cast method with a class representing your data. Let's take the following PKL code:

myUser {
    id = 1
    name = "John Doe"
    address {
        street = "123 Main St"
        city = "Springfield"
        state = "IL"
        zip = "62701"
    }
}

You can cast this to a User class like this:

use Phikl\Pkl;

class User
{
    public int $id;
    public string $name;
    public Address $address;
}

class Address
{
    public string $street;
    public string $city;
    public string $state;
    public string $zip;
}

$module = Pkl::eval('config/user.pkl');
$user = $module->get('myUser')->cast(User::class);

You can also pass User::class as the second argument to the eval method. This will automatically cast the module to the given class. Beware that it returns an array indexed by the PKL instance name:

use Phikl\Pkl;

// ...

$user = Pkl::eval('config/user.pkl', User::class)['myUser'];

The PklProperty Attribute

You can use the PklProperty attribute to specify the name of the property in the PKL file. This is useful when the property name in the PKL file is different from the property name in the PHP class. Let's take the following PKL code:

myUser {
    id = 1
    name = "John Doe"
    address {
        street = "123 Main St"
        city = "Springfield"
        state = "IL"
        zip = "62701"
    }
}

You can define a User class like this:

use Phikl\PklProperty;

class User
{
    #[PklProperty('id')]
    public int $userId;

    #[PklProperty('name')]
    public string $userName;

    public Address $address;
}

When casting, the PklProperty attribute will be used to map the property name in the PKL file to the property name in the PHP class.

Caching

You can (and should) cache the PKL modules to improve performance. This is especially useful when evaluating the same PKL file multiple times.

⚠️ Using Phikl with the cache avoids the PKL CLI tool to be executed to evaluate modules and should be done when deploying your application for better performances.

Warmup the Cache

You can use the warmup command to dump the PKL modules to a cache file by default. Phikl will then use the cache file automatically when evaluating a PKL file. If the PKL file is not found in the cache, Phikl will evaluate the PKL file on the go.

Phikl will go through all .pkl files of your project and dump them to the cache file.

Here's an example of how to use the warmup command:

vendor/bin/phikl warmup

# you can also specify the file if you want to use a custom location
# don't forget to set the `PHIKL_CACHE_FILE` environment variable
vendor/bin/phikl warmup --cache-file=cache/pkl.cache

If you need to validate a cache file, you can do so by using the validate-cache command:

vendor/bin/phikl validate-cache

# optionally, set the `PHIKL_CACHE_FILE` environment variable
# or use the `--cache-file` option
vendor/bin/phikl validate-cache --cache-file=.cache/.phikl

Here are a few things to note about Phikl cache:

• You can disable the cache by calling Pkl::toggleCache(false), which is useful for development but highly discouraged in production
• Phikl will automatically refresh the cache if a PKL module is modified since last warmup
• Any corrupted cache entry will be automatically refreshed

Cache Backends

If you have your own cache system, you can use the Pkl::setCache() method to set the cache system to use. You can pass it any instance of compliant PSR-16 cache system implementing Psr\SimpleCache\CacheInterface. This is useful you want to use, for example, a Redis server as a cache system for your Pkl modules.

Phikl comes with the following cache backends:

• PersistentCache, which is the default one used by Phikl. It uses a file to store the cache ;
• ApcuCacheAdapter, which uses the APCu extension to store the cache in memory ;
• MemcachedCacheAdapter, which uses the Memcached extension to store the cache in memory.