Mutations

Mutation is just a field of a regular Object Type with arguments. For GraphQL PHP runtime there is no difference between query fields with arguments and mutations. They are executed almost identically. To some extent, Mutation is just a convention described in the GraphQL spec.

Here is an example of a mutation operation:

mutation CreateReviewForEpisode($ep: EpisodeInput!, $review: ReviewInput!) {
  createReview(episode: $ep, review: $review) {
    stars
    commentary
  }
}

To execute such a mutation, you need Mutation type at the root of your schema:

<?php
use GraphQL\Type\Definition\Type;
use GraphQL\Type\Definition\ObjectType;

$myMutationType = new ObjectType([
    'name' => 'Mutation',
    'fields' => [
        // List of mutations:
        'createReview' => [
            'args' => [
                'episode' => Type::nonNull($episodeInputType),
                'review' => Type::nonNull($reviewInputType)
            ],
            'type' => new ObjectType([
                'name' => 'CreateReviewOutput',
                'fields' => [
                    'stars' => ['type' => Type::int()],
                    'commentary' => ['type' => Type::string()]
                ]
            ]),
        ],
        // ... other mutations
    ]
]);

As you can see, the only difference from regular object type is the semantics of field names (verbs vs nouns).

Also as we see arguments can be of complex types. To leverage the full power of mutations (and field arguments in general) you must learn how to create complex input types.

About Input and Output Types

All types in GraphQL are of two categories: input and output.

Obviously, NonNull and List types belong to both categories depending on their inner type.

Until now all examples of field arguments in this documentation were of Scalar or Enum types. But you can also pass complex objects.

This is particularly valuable in case of mutations, where input data might be rather complex.

Input Object Type

GraphQL specification defines Input Object Type for complex inputs. It is similar to ObjectType except that it's fields have no args or resolve options and their type must be input type.

In graphql-php Input Object Type is an instance of GraphQL\Type\Definition\InputObjectType (or one of it subclasses) which accepts configuration array in constructor:

<?php
use GraphQL\Type\Definition\Type;
use GraphQL\Type\Definition\InputObjectType;

$filters = new InputObjectType([
    'name' => 'StoryFiltersInput',
    'fields' => [
        'author' => [
            'type' => Type::id(),
            'description' => 'Only show stories with this author id'
        ],
        'popular' => [
            'type' => Type::boolean(),
            'description' => 'Only show popular stories (liked by several people)'
        ],
        'tags' => [
            'type' => Type::listOf(Type::string()),
            'description' => 'Only show stories which contain all of those tags'
        ]
    ]
]);

Every field may be of other InputObjectType (thus complex hierarchies of inputs are possible)

Configuration options

The constructor of InputObjectType accepts array with only 3 options:

Option Type Notes
name string Required. Unique name of this object type within Schema
fields array or callable Required. An array describing object fields or callable returning such an array (see below).
description string Plain-text description of this type for clients (e.g. used by GraphiQL for auto-generated documentation)

Every field is an array with following entries:

Option Type Notes
name string Required. Name of the input field. When not set - inferred from fields array key
type Type Required. Instance of one of Input Types (Scalar, Enum, InputObjectType + any combination of those with nonNull and listOf modifiers)
description string Plain-text description of this input field for clients (e.g. used by GraphiQL for auto-generated documentation)
defaultValue scalar Default value of this input field

Using Input Object Type

In the example above we defined our InputObjectType. Now let's use it in one of field arguments:

<?php
use GraphQL\Type\Definition\Type;
use GraphQL\Type\Definition\ObjectType;

$queryType = new ObjectType([
    'name' => 'Query',
    'fields' => [
        'stories' => [
            'type' => Type::listOf($storyType),
            'args' => [
                'filters' => [
                    'type' => Type::nonNull($filters),
                    'defaultValue' => [
                        'popular' => true
                    ]
                ]
            ],
            'resolve' => function($rootValue, $args) {
                return DataSource::filterStories($args['filters']);
            }
        ]
    ]
]);

(note that you can define defaultValue for fields with complex inputs as associative array).

Then GraphQL query could include filters as literal value:

{
    stories(filters: {author: "1", popular: false})
}

Or as query variable:

query($filters: StoryFiltersInput!) {
    stories(filters: $filters)
}
$variables = [
    'filters' => [
        "author" => "1",
        "popular" => false
    ]
];

graphql-php will validate the input against your InputObjectType definition and pass it to your resolver as $args['filters']