JSONSchema to PHP class converter

Build PHP classes from JSON schemas automatically.

Example

Consider a simple JSON schema (ironically stored in YAML format), stored in a file example.yaml:

required:
  - givenName
  - familyName
properties:
  givenName:
    type: string
  familyName:
    type: string
  hobbies:
    type: array
    items:
      type: string
  location:
    properties:
      country:
        type: string
      city:
        type: string 

Using this converter, you can automatically generate PHP classes from this schema with accessor and conversion functions:

$ vendor/bin/s2c generate:fromschema --class User ./example.yaml src/Target

This command will automatically try to infer a PHP target namespace from your composer.json file and automatically create the appropriate PHP classes:

$ find src/Target
src/Target
src/Target/User.php
src/Target/UserLocation.php

Then, use the classes in your code:

$userData = json_decode("user.json", true);
$user = \MyNamespace\Target\User::buildFromInput($userData);

echo "Hello, " . $user->getGivenName() . "\n";

Compatibility

This tool requires PHP 8.2 or newer to run.

The generated code can be backwards-compatible up until PHP 5.6. Use the --target-php flag to set the desired PHP version that the generated code should be compatible with. When using a configuration file, use the targetPHPVersion property.

Creation result

The generated classes have these features:

• The class namespace can either be specified via command-line (--target-namespace), specification file (targetNamespace). If neither is specified, the generator will inspect the composer.json of your project, look for any PSR-4 configuration and infer the namespace from there.
• The main object's name is defined by the command-line (--class) or the specification file.
• Sub-object's names are taken from the property name.
• Array items are suffixed 'Item'.
• OneOf alternatives are suffixed 'AlternativeX', with X being an incremented integer.
• The constructor has arguments for all required properties in the schema.
• All properties are private, with getter methods for access, and explicit type declarations for the return value (in PHP5 mode, only PHPDoc is used).
• Static function buildFromInput(array $data) accepts an array (using json_decode('{}', true)), validates it according to the schema and creates the full object tree as return value. An additional mapping step is not required.
• Function toJson() returns a plain array ready for json_encode().
• Writing to any object's properties is done immutably by using withX() (or withoutX() for optional values). This will return a new instance of that object with the value changed.

As an example, a shortened version with all comments removed, from the above schema shows the location, only containing the city (country is behaving the same, but with a different name)

class UserLocation
{
    private static array $schema = array(
        'properties' => array(
            'city' => array(
                'type' => 'string',
            ),
        ),
    );

    private ?string $country = null;

    private ?string $city = null;

    public function __construct()
    {
    }

    public function getCity() : ?string
    {
        return $this->city;
    }

    public function withCity(string $city) : self
    {
        $validator = new \JsonSchema\Validator();
        $validator->validate($city, static::$schema['properties']['city']);
        if (!$validator->isValid()) {
            throw new \InvalidArgumentException($validator->getErrors()[0]['message']);
        }

        $clone = clone $this;
        $clone->city = $city;

        return $clone;
    }

    public function withoutCity() : self
    {
        $clone = clone $this;
        unset($clone->city);

        return $clone;
    }

    public static function buildFromInput(array $input) : UserLocation
    {
        static::validateInput($input);

        $city = null;
        if (isset($input['city'])) {
            $city = $input['city'];
        }

        $obj = new static();
        $obj->city = $city;
        return $obj;
    }

    public function toJson() : array
    {
        $output = [];
        if (isset($this->city)) {
            $output['city'] = $this->city;
        }

        return $output;
    }

    public static function validateInput(array $input, bool $return = false) : bool
    {
        $validator = new \JsonSchema\Validator();
        $validator->validate($input, static::$schema);

        if (!$validator->isValid() && !$return) {
            $errors = array_map(function($e) {
                return $e["property"] . ": " . $e["message"];
            }, $validator->getErrors());
            throw new \InvalidArgumentException(join(", ", $errors));
        }

        return $validator->isValid();
    }

    public function __clone()
    {
    }
}

Installation

Install using Composer:

$ composer require --dev helmich/schema2class

Using configuration files

In many projects, you're going to want to keep an evolving JSON schema in sync with the generated PHP classes continuously. For this reason, S2C allows you to create a configuration file .s2c.yaml that stores the most common conversion options:

targetPHPVersion: "7.4"
files:
- input: src/Spec/Spec.yaml
  className: Specification
  targetDirectory: src/Spec

You can store your local configuration in this yaml file and start the generation process by calling

s2c generate:fromspec

This will scan for .s2c.yaml in the current directory and use it's parameters. If you need to have different files for multiple schemas, you can provide a config file as a parameter.