add first basic hello world graphql server written with reactphp to api

Author: Florian Engelhardt

api/app.php

@@ -0,0 +1,72 @@
+<?php
+declare(strict_types=1);
+
+use Psr\Http\Message\ServerRequestInterface;
+use React\EventLoop\Factory;
+use React\Http\Response;
+use React\Http\Server;
+
+use GraphQL\GraphQL;
+use GraphQL\Type\Schema;
+use GraphQL\Executor\ExecutionResult;
+use GraphQL\Executor\Promise\Adapter\ReactPromiseAdapter;
+
+use GraphQL\Type\Definition\ObjectType;
+use GraphQL\Type\Definition\Type;
+
+require __DIR__ . '/vendor/autoload.php';
+
+$queryType = new ObjectType([
+    'name' => 'Query',
+    'fields' => [
+        'echo' => [
+            'type' => Type::string(),
+            'args' => [
+                'message' => Type::nonNull(Type::string()),
+            ],
+            'resolve' => function($root, $args) {
+                return $root['prefix'] . $args['message'];
+            }
+        ]/*,
+        'echo' => [
+            'type' => Type::string(),
+            'args' => [
+                'message' => Type::nonNull(Type::string()),
+            ],
+            'resolve' => function ($root, $args) {
+                return $root['prefix'] . $args['message'];
+            }
+        ],
+        */
+    ],
+]);
+
+$schema = new Schema([
+    'query' => $queryType
+]);
+
+$loop = Factory::create();
+$react = new ReactPromiseAdapter();
+
+$server = new Server(function (ServerRequestInterface $request) use ($schema, $react) {
+    $rawInput = (string)$request->getBody();
+    $input = json_decode($rawInput, true);
+    $query = $input['query'];
+    $variableValues = isset($input['variables']) ? $input['variables'] : null;
+    $rootValue = ['prefix' => 'You said: '];
+    $promise = GraphQL::promiseToExecute($react, $schema, $query, $rootValue, null, $variableValues);
+    return $promise->then(function(ExecutionResult $result) {
+        $output = $result->toArray();
+        return new Response(
+            200,
+            array(
+                'Content-Type' => 'application/json'
+            ),
+            json_encode($output)
+        );
+    });
+});
+$socket = new \React\Socket\Server('0.0.0.0:3000', $loop);
+$server->listen($socket);
+echo 'Listening on ' . str_replace('tcp:', 'http:', $socket->getAddress()) . PHP_EOL;
+$loop->run();