fix psalm errors

composer.json

@@ -28,14 +28,16 @@
     "psr/http-message": "^1",
     "react/http": "^1.6",
     "react/promise": "^2.9",
+    "amphp/http-server": "^2.1",
     "rector/rector": "^0.15.18",
     "symfony/polyfill-php81": "^1.23",
     "symfony/var-exporter": "^5 || ^6",
     "thecodingmachine/safe": "^1.3 || ^2"
   },
   "suggest": {
     "psr/http-message": "To use standard GraphQL server",
-    "react/promise": "To leverage async resolving on React PHP platform"
+    "react/promise": "To leverage async resolving on React PHP platform",
+    "amphp/http-server": "To leverage async resolving with webserver on AMPHP platform"
   },
   "autoload": {
     "psr-4": {

examples/04-async-php/amphp/event-loop/graphql.php

@@ -13,7 +13,13 @@
 $schema = require_once __DIR__ . '/../schema.php';
 
 Loop::run(function () use ($schema): void {
-    $input = json_decode(file_get_contents('php://input'), true);
+    $content = file_get_contents('php://input');
+    $input = '';
+
+    if ($content !== false) {
+        $input = json_decode($content, true);
+    }
+
     $promise = GraphQL::promiseToExecute(
         new AmpPromiseAdapter(),
         $schema,

examples/04-async-php/amphp/http-server/graphql.php

@@ -27,14 +27,14 @@
         $query = $input['query'];
         $variableValues = $input['variables'] ?? null;
         $promise = GraphQL::promiseToExecute(new AmpPromiseAdapter(), $schema, $query, [], null, $variableValues);
-        $promise = $promise->then(fn(ExecutionResult $result): Response =>
-            new Response(
+        $promise = $promise->then(function(ExecutionResult $result): Response {
+            $data = json_encode($result->toArray());
+            return new Response(
                 200,
                 ['Content-Type' => 'application/json'],
-                json_encode($result->toArray())
-            )
-        );
-
+                $data !== false ? $data : null
+            );
+        });
         return $promise->adoptedPromise;
     }), new Psr\Log\NullLogger);