GqlTypeExample.php

<?php
class HumanType 
{
    public function getDefinition() 
    {
        return '
            type Human : Character {
              id: String!
              name: String
              friends: [Character] @resolveMethod("getFriends")
              appearsIn: [Episode]
              homePlanet: String
            }
        ';
    }

    public function getFriends() 
    {
        //resolve friends
    }
}