Schema Definition Language

The schema definition language is a convenient way to define your schema, especially with IDE autocompletion and syntax validation.

You can define this separately from your PHP code. An example for a schema.graphql file might look like this:

type Query {
  greetings(input: HelloInput!): String!
}

input HelloInput {
  firstName: String!
  lastName: String
}

To create an executable schema instance from this file, use GraphQL\Utils\BuildSchema:

use GraphQL\Utils\BuildSchema;

$contents = file_get_contents('schema.graphql');
$schema = BuildSchema::build($contents);

By default, such a schema is created without any resolvers. We have to rely on the default field resolver and the root value to execute queries against this schema.

Defining resolvers

To enable Interfaces, Unions, and custom field resolvers, you can pass the second argument callable $typeConfigDecorator to BuildSchema::build().

It accepts a callable that receives the default type config produced by the builder and is expected to add missing options like resolveType for interface types or resolveField for object types.

use GraphQL\Utils\BuildSchema;
use GraphQL\Language\AST\TypeDefinitionNode;

$typeConfigDecorator = function (array $typeConfig, TypeDefinitionNode $typeDefinitionNode): array {
    $name = $typeConfig['name'];
    // ... add missing options to $typeConfig based on type $name
    return $typeConfig;
};

$contents = file_get_contents('schema.graphql');
$schema = BuildSchema::build($contents, $typeConfigDecorator);

You can learn more about using $typeConfigDecorator in examples/05-using-typeConfigDecorator-with-SDL

Performance considerations

Method BuildSchema::build() produces a lazy schema automatically, so it works efficiently even with huge schemas.

However, parsing the schema definition file on each request is suboptimal. It is recommended to cache the intermediate parsed representation of the schema for the production environment:

use GraphQL\Language\Parser;
use GraphQL\Utils\BuildSchema;
use GraphQL\Utils\AST;

$cacheFilename = 'cached_schema.php';

if (!file_exists($cacheFilename)) {
    $document = Parser::parse(file_get_contents('./schema.graphql'));
    file_put_contents($cacheFilename, "<?php\nreturn " . var_export(AST::toArray($document), true) . ";\n");
} else {
    $document = AST::fromArray(require $cacheFilename); // fromArray() is a lazy operation as well
}

$typeConfigDecorator = function () {};
$schema = BuildSchema::build($document, $typeConfigDecorator);