add more documentation to the source code

Author: Florian Engelhardt

api/app.php

@@ -20,13 +20,18 @@
 
 require __DIR__ . '/schema.php';
 
+// GraphQL-PHP needs to know which async implementation we are using
+// in this case it's ReactPHP
 $react = new ReactPromiseAdapter();
 
 $server = new Server(function (ServerRequestInterface $request) use ($schema, $react) {
+    // GraphQL Input is "just" a JSON-String
     $input = json_decode((string)$request->getBody(), true);
     $query = $input['query'];
     $variableValues = isset($input['variables']) ? $input['variables'] : null;
+    // just pass query and variables to the GraphQL lib
     $promise = GraphQL::promiseToExecute($react, $schema, $query, [], null, $variableValues);
+    // promiseToExecute will return a ReactPHP Promise, so we can register our then callback
     return $promise->then(function(ExecutionResult $result) {
         $output = $result->toArray();
         return new Response(

api/schema.php

@@ -6,6 +6,7 @@
 use GraphQL\Type\Definition\ObjectType;
 use GraphQL\Type\Definition\Type;
 
+// the resolver function may return a string or a ReactPHP Promise
 $productResolver = function ($review) use ($browser) {
     return $browser->get('http://product-service:3000/')->then(function($response) {
         $rawBody = (string)$response->getBody();
@@ -20,6 +21,8 @@
     });
 };
 
+// return type definitions
+
 $productType = new ObjectType([
     'name' => 'Product',
     'fields' => [
@@ -57,6 +60,8 @@
     ]
 ]);
 
+// query defintion
+
 $query = new ObjectType([
     'name' => 'Query',
     'fields' => [
@@ -87,6 +92,8 @@
     ],
 ]);
 
+// schema packs query and types together
+
 $schema = new Schema([
     'query' => $query,
     'types' => [