This library provides you simple way to implement GraphQL API using it's schema definition language.

GraphQL uses resolvers functions in order to fetch data. It acts as function, which receives some input and returns value according to schema.

public function resolveUserProfile(array $args)
{
    ['id' => $id] = $args;
    
    return $this->db->fetchUser($id);
}

You could specify resolvers for any field in your schema. If resolver for some field is not provided, then default resolver will be used.

Default resolver is used to fetch single fields out of values, provided by resolvers higher in hierarchy. You could treat it as leaf resolver in your tree.

It could retrieve values of fields from both arrays and objects. If object is given, and it has accessor for needed field, then it would be called. You could also process arguments for given field.

For example, in parent resolver we returned user profile object, which should have userPic field. We also want to specify size of picture in order to generate thumbnail. Then we could just add method userPic(int $width, int $height) or getUserPic(int $width, int $height) in our object:

class UserProfile
{
    // ...
    public function userPic(int $width, int $height): Thumb
    {
        return Thumb::forImage($this->userPic, $width, $height);
    }
}