Given a Mutation Name and Config array, this adds a Mutation to the Schema

register_graphql_mutation( string $mutation_name, array $config );

Parameters

$mutation_name (string): The name of the mutation
$config (array): Configuration for the mutation
- $description (string): Description of the mutation type.
- $inputFields (array): The input fields for the mutation
  - $type (string): The name of the Type in the Schema the field should accept. Note: ObjectTypes cannot be used as Input Types.
  - $description (string): The field description.
- $outputFields (array): The output field for the mutation (what can be asked for in response)
- $mutateAndGetPayload (function): How the mutation should resolve

Source

File: access-functions.php

Example

Here is a basic example of registering a mutation:

# This function registers a mutation to the Schema.
# The first argument, in this case `exampleMutation`, is the name of the mutation in the Schema
# The second argument is an array to configure the mutation.
# The config array accepts 3 key/value pairs for: inputFields, outputFields and mutateAndGetPayload.
register_graphql_mutation( 'exampleMutation', [

	# inputFields expects an array of Fields to be used for inputting values to the mutation
	'inputFields'         => [
		'exampleInput' => [
			'type' => 'String',
			'description' => __( 'Description of the input field', 'your-textdomain' ),
		]
	],

	# outputFields expects an array of fields that can be asked for in response to the mutation
	# the resolve function is optional, but can be useful if the mutateAndPayload doesn't return an array
	# with the same key(s) as the outputFields
	'outputFields'        => [
		'exampleOutput' => [
			'type' => 'String',
			'description' => __( 'Description of the output field', 'your-textdomain' ),
			'resolve' => function( $payload, $args, $context, $info ) {
                   		return isset( $payload['exampleOutput'] ) ? $payload['exampleOutput'] : null;
			}
		]
	],

	# mutateAndGetPayload expects a function, and the function gets passed the $input, $context, and $info
	# the function should return enough info for the outputFields to resolve with
	'mutateAndGetPayload' => function( $input, $context, $info ) {
		// Do any logic here to sanitize the input, check user capabilities, etc
		$exampleOutput = null;
		if ( ! empty( $input['exampleInput'] ) ) {
			$exampleOutput = 'Your input was: ' . $input['exampleInput'];
		}
		return [
			'exampleOutput' => $exampleOutput,
		];
	}
] );

Registering the above mutation would allow for the following mutation to be executed:

mutation {
	exampleMutation(
		input: { clientMutationId: "example", exampleInput: "Test..." }
	) {
		clientMutationId
		exampleOutput
	}
}

And the following response would be provided:

{
	"data": {
		"exampleMutation": {
			"clientMutationId": "example",
			"exampleOutput": "Your input was: Test..."
		}
	}
}