graphql-php/README.md

graphql-php

Work in progress. Things may change before first stable release.

This is a PHP port of GraphQL reference implementation based on the specification and the reference implementation in JavaScript.

This implementation will follow JavaScript version as close as possible until GraphQL itself stabilizes.

Current status: version 0.4 supports all features described by specification. corresponding graphql-js commit: cf50cc3a304faff9a4215cd121a548e65794a089 (v0.4.2 2015-08-14).

Table of Contents

• Overview
• Installation
• Type System
  • Internal Types
  • Enums
  • Interfaces
  • Objects
  • Unions (TODOC)
  • Fields
• Schema definition
• Query Resolution and Data Fetching
• HTTP endpoint example
• More Examples

Overview

GraphQL is intended to be a replacement for REST APIs. Read more about rationale behind it.

This PHP implementation is a thin wrapper around your existing data layer and business logic. It doesn't dictate how these layers are implemented or which storage engines are used. Instead it provides tools for creating API for your existing app. These tools include:

• Type system
• Schema validation and introspection
• Ability to parse and execute GraphQL queries against type system

Actual data fetching has to be implemented on the user land.

Installing graphql-php

$> curl -sS https://getcomposer.org/installer | php
$> php composer.phar require webonyx/graphql-php='dev-master'

Requirements

PHP >=5.4

Getting Started

First, make sure to read Getting Started section of GraphQL documentation. Examples below implement the type system described in this document.

Type System

To start using GraphQL you are expected to implement a Type system.

GraphQL PHP provides several kinds of types to build hierarchical type system: scalar, enum, object, interface, union, listOf, nonNull.

Internal types

Only several scalar types are implemented out of the box: ID, String, Int, Float, Boolean

As well as two internal modifier types: ListOf and NonNull.

All internal types are exposed as static methods of GraphQL\Type\Definition\Type class:

use GraphQL\Type\Definition\Type;

// Internal Scalar types:
Type::string();  // String type
Type::int();     // Int type
Type::float();   // Float type
Type::boolean(); // Boolean type
Type::id();      // ID type

// Internal wrapping types:
Type::nonNull(Type::string()) // String! type
Type::listOf(Type::string())  // String[] type

Other types must be implemented by your application. Most often you will work with enum, object, interface and union type kinds to build a type system.

Enums

Enum types represent a set of allowed values for an object field. Let's define enum type describing the set of episodes of original Star Wars trilogy:

use GraphQL\Type\Definition\EnumType;

/**
 * The original trilogy consists of three movies.
 *
 * This implements the following type system shorthand:
 *   enum Episode { NEWHOPE, EMPIRE, JEDI }
 */
$episodeEnum = new EnumType([
    'name' => 'Episode',
    'description' => 'One of the films in the Star Wars Trilogy',
    'values' => [
        'NEWHOPE' => [
            'value' => 4,
            'description' => 'Released in 1977.'
        ],
        'EMPIRE' => [
            'value' => 5,
            'description' => 'Released in 1980.'
        ],
        'JEDI' => [
            'value' => 6,
            'description' => 'Released in 1983.'
        ],
    ]
]);

Interfaces

Next, let's define a Character interface, describing characters of original Star Wars trilogy:

use GraphQL\Type\Definition\InterfaceType;
use GraphQL\Type\Definition\Type;

// Implementor types (will be defined in next examples):
$humanType = null;
$droidType = null;

/**
 * Characters in the Star Wars trilogy are either humans or droids.
 *
 * This implements the following type system shorthand:
 *   interface Character {
 *     id: String!
 *     name: String
 *     friends: [Character]
 *     appearsIn: [Episode]
 *   }
 */
$characterInterface = new InterfaceType([
    'name' => 'Character',
    'description' => 'A character in the Star Wars Trilogy',
    'fields' => [
        'id' => [
            'type' => Type::nonNull(Type::string()),
            'description' => 'The id of the character.',
        ],
        'name' => [
            'type' => Type::string(),
            'description' => 'The name of the character.'
        ],
        'friends' => [
            'type' => function () use (&$characterInterface) {
                return Type::listOf($characterInterface);
            },
            'description' => 'The friends of the character.',
        ],
        'appearsIn' => [
            'type' => Type::listOf($episodeEnum),
            'description' => 'Which movies they appear in.'
        ]
    ],
    'resolveType' => function ($obj) use (&$humanType, &$droidType) {
        $humans = StarWarsData::humans();
        $droids = StarWarsData::droids();
        if (isset($humans[$obj['id']])) {
            return $humanType;
        }
        if (isset($droids[$obj['id']])) {
            return $droidType;
        }
        return null;
    },
]);

As you can see type may be optionally defined as callback that returns actual type at runtime. (see Fields section for details)

In this example field friends represents a list of characterInterface. Since at the moment of type definition characterInterface is still not defined, we pass in closure that will return this type at runtime.

Interface definition options:

Option	Type	Notes
name	string	Required. Unique name of this interface type within Schema
fields	array	Required. List of fields required to be defined by interface implementors. See Fields section for available options.
description	string	Textual description of this interface for clients
resolveType	callback(value) => objectType	Any callable that receives data from data layer of your application and returns concrete interface implementor for that data.

Notes:

1. If resolveType option is omitted, GraphQL PHP will loop through all interface implementors and use their isTypeOf() method to pick the first suitable one. This is obviously less efficient than single resolveType call. So it is recommended to define resolveType when possible.

2. Interface types do not participate in data fetching. They just resolve actual object type which will be asked for data when GraphQL query is executed.

Objects

Now let's define Human type that implements CharacterInterface from example above:

use GraphQL\Type\Definition\ObjectType;
use GraphQL\Type\Definition\Type;

/**
 * We define our human type, which implements the character interface.
 *
 * This implements the following type system shorthand:
 *   type Human : Character {
 *     id: String!
 *     name: String
 *     friends: [Character]
 *     appearsIn: [Episode]
 *   }
 */
$humanType = new ObjectType([
    'name' => 'Human',
    'description' => 'A humanoid creature in the Star Wars universe.',
    'fields' => [
        'id' => [
            'type' => Type::nonNull(Type::string()),
            'description' => 'The id of the human.',
        ],
        'name' => [
            'type' => Type::string(),
            'description' => 'The name of the human.',
        ],
        'friends' => [
            'type' => Type::listOf($characterInterface),
            'description' => 'The friends of the human',
            'resolve' => function ($human) {
                return StarWarsData::getFriends($human);
            },
        ],
        'appearsIn' => [
            'type' => Type::listOf($episodeEnum),
            'description' => 'Which movies they appear in.'
        ],
        'homePlanet' => [
            'type' => Type::string(),
            'description' => 'The home planet of the human, or null if unknown.'
        ],
    ],
    'interfaces' => [$characterInterface]
]);

Object definition options

Option	Type	Notes
name	string	Required. Unique name of this object type within Schema
fields	array	Required. List of fields describing object properties. See Fields section for available options.
description	string	Textual description of this type for clients
interfaces	array or callback() => ObjectType[]	List of interfaces implemented by this type (or callback returning list of interfaces)
isTypeOf	callback($value, GraphQL\Type\Definition\ResolveInfo $info)	Callback that takes $value provided by your data layer and returns true if that $value qualifies for this type

Notes:

1. Both object types and interface types define set of fields which can have their own types. That's how type composition is implemented.

2. Object types are responsible for data fetching. Each of their fields may have optional resolve callback option. This callback takes $value that corresponds to instance of this type and returns data accepted by type of given field. If resolve option is not set, GraphQL will try to get data from $value[$fieldName].

3. resolve callback is a place where you can use your existing data fetching logic.

4. Other ObjectType mentioned in examples is Droid. Check out tests for this type: https://github.com/webonyx/graphql-php/blob/master/tests/StarWarsSchema.php

Unions

TODOC

Fields

Fields are parts of Object and Interface type definitions.

Allowed Field definition options:

Option	Type	Notes
name	string	Required. Name of the field. If not set - GraphQL will look use key of fields array on type definition.
type	Type or callback() => Type	Required. One of internal or custom types. Alternatively - callback that returns type.
args	array	Array of possible type arguments. Each entry is expected to be an array with following keys: name (string), type (Type or callback() => Type), defaultValue (any)
resolve	callback($value, $args, ResolveInfo $info) => $fieldValue	Function that receives $value of parent type and returns value for this field.
description	string	Field description for clients
deprecationReason	string	Text describing why this field is deprecated. When not empty - field will not be returned by introspection queries (unless forced)

Schema

After all of your types are defined, you must define schema. Schema consists of two special root-level types: Query and Mutation

Query type is a surface of your read API. Mutation type exposes write API by declaring all possible mutations in your app.

Example schema:

use GraphQL\Type\Definition\ObjectType;
use GraphQL\Type\Definition\Type;
use GraphQL\Schema;

/**
 * This is the type that will be the root of our query, and the
 * entry point into our schema. It gives us the ability to fetch
 * objects by their IDs, as well as to fetch the undisputed hero
 * of the Star Wars trilogy, R2-D2, directly.
 *
 * This implements the following type system shorthand:
 *   type Query {
 *     hero(episode: Episode): Character
 *     human(id: String!): Human
 *     droid(id: String!): Droid
 *   }
 *
 */
$queryType = new ObjectType([
    'name' => 'Query',
    'fields' => [
        'hero' => [
            'type' => $characterInterface,
            'args' => [
                'episode' => [
                    'description' => 'If omitted, returns the hero of the whole saga. If provided, returns the hero of that particular episode.',
                    'type' => $episodeEnum
                ]
            ],
            'resolve' => function ($root, $args) {
                return StarWarsData::getHero(isset($args['episode']) ? $args['episode'] : null);
            },
        ],
        'human' => [
            'type' => $humanType,
            'args' => [
                'id' => [
                    'name' => 'id',
                    'description' => 'id of the human',
                    'type' => Type::nonNull(Type::string())
                ]
            ],
            'resolve' => function ($root, $args) {
                $humans = StarWarsData::humans();
                return isset($humans[$args['id']]) ? $humans[$args['id']] : null;
            }
        ],
        'droid' => [
            'type' => $droidType,
            'args' => [
                'id' => [
                    'name' => 'id',
                    'description' => 'id of the droid',
                    'type' => Type::nonNull(Type::string())
                ]
            ],
            'resolve' => function ($root, $args) {
                $droids = StarWarsData::droids();
                return isset($droids[$args['id']]) ? $droids[$args['id']] : null;
            }
        ]
    ]
]);

// TODOC
$mutationType = null;

$schema = new Schema($queryType, $mutationType);

Notes:

1. Query is a regular object type.

2. Fields of this type represent all possible root-level queries to your API.

3. Fields can have args, so that your queries could be dynamic (see Fields section).

Query Resolution

Resolution is a cascading process that starts from root Query type.

In our example Query type exposes field human that expects id argument. Say we receive following GraphQL query that requests data for Luke Skywalker:

query FetchLukeQuery {
  human(id: "1000") {
    name
    friends {
      name
    }
  }
}

And that's how our data for Luke looks like (in some internal storage):

$lukeData = [
    'id' => '1000',
    'name' => 'Luke Skywalker',
    'friends' => ['1002', '1003', '2000', '2001'],
    'appearsIn' => [4, 5, 6],
    'homePlanet' => 'Tatooine',
]

What happens:

1. GraphQL query is parsed and validated against schema (it happens in GraphQL\GraphQL::execute() method)
2. GraphQL executor detects that field human of Human type is requested at root Query level
3. It calls resolve(null, ['id' => 1000]) on this field (note first argument is null at the root level)
4. resolve callback of human field fetches our data by id and returns it
5. Since field human is expected to return type Human GraphQL traverses all requested fields of type Human and matches them against $lukeData
6. Requested field name on Human type does not provide any resolve callback, so GraphQL simply resolves it as $lukeData['name']
7. Requested field friend has resolve callback, so it is called: resolve($lukeData, /*args*/ [], ResolveInfo $info)
8. Callback fetches data for all $lukeData['friends'] and returns [$friend1002, $friend1003, ...] where each entry contains array with same structure as $lukeData
9. GraphQL executor repeats these steps until all requested leaf fields are reached
10. Final result is composed and returned:

[
    'human' => [
        'name' => 'Luke Skywalker',
        'friends' => [
            ['name' => 'Han Solo'],
            ['name' => 'Leia Organa'],
            ['name' => 'C-3PO'],
            ['name' => 'R2-D2'],
        ]
    ]
]

HTTP endpoint

Specification for GraphQL HTTP endpoint is still under development. But you can use following naive example to build your own custom HTTP endpoint that is ready to accept GraphQL queries:

use GraphQL\GraphQL;
use \Exception;

if (isset($_SERVER['CONTENT_TYPE']) && $_SERVER['CONTENT_TYPE'] === 'application/json') {
    $rawBody = file_get_contents('php://input')
    $data = json_decode($rawBody ?: '', true);
} else {
    $data = $_POST;
}

$requestString = isset($data['query']) ? $data['query'] : null;
$operationName = isset($data['operation']) ? $data['operation'] : null;
$variableValues = isset($data['variables']) ? $data['variables'] : null;

try {
    // Define your schema:
    $schema = MyApp\Schema::build();
    $result = GraphQL::execute(
        $schema,
        $requestString,
        /* $rootValue */ null,
        $variableValues,
        $operationName
    );
} catch (Exception $exception) {
    $result = [
        'errors' => [
            ['message' => $exception->getMessage()]
        ]
    ];
}

header('Content-Type: application/json');
echo json_encode($result);

More Examples

Make sure to check tests for more usage examples.