About Input and Output Types

GraphQL receives data from clients via Field Arguments.

Both - fields and arguments require type option in definition. But expected value of this option is different for fields and arguments, as in GraphQL argument is conceptually input while field is conceptually output.

Consequentially 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 easily pass complex objects.

This is particularly valuable in the 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:

$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

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 callback returning array Required. Array describing object fields (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 List 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:

$queryType = new ObjectType([
    'name' => 'Query',
    'fields' => [
        'stories' => [
            'type' => Type::listOf($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']