Merge pull request guzzle#105 from jimcottrell/master

Add explicit object checks before calling method_exists()

src/FulfilledPromise.php

@@ -13,7 +13,7 @@ class FulfilledPromise implements PromiseInterface
 
     public function __construct($value)
     {
-        if (method_exists($value, 'then')) {
+        if (is_object($value) && method_exists($value, 'then')) {
             throw new \InvalidArgumentException(
                 'You cannot create a FulfilledPromise with a promise.');
         }

src/Promise.php

@@ -148,7 +148,7 @@ private function settle($state, $value)
 
         // If the value was not a settled promise or a thenable, then resolve
         // it in the task queue using the correct ID.
-        if (!method_exists($value, 'then')) {
+        if (!is_object($value) || !method_exists($value, 'then')) {
             $id = $state === self::FULFILLED ? 1 : 2;
             // It's a success, so resolve the handlers in the queue.
             queue()->add(static function () use ($id, $value, $handlers) {

src/RejectedPromise.php

@@ -13,7 +13,7 @@ class RejectedPromise implements PromiseInterface
 
     public function __construct($reason)
     {
-        if (method_exists($reason, 'then')) {
+        if (is_object($reason) && method_exists($reason, 'then')) {
             throw new \InvalidArgumentException(
                 'You cannot create a RejectedPromise with a promise.');
         }

src/functions.php

@@ -70,7 +70,7 @@ function promise_for($value)
     }
 
     // Return a Guzzle promise that shadows the given promise.
-    if (method_exists($value, 'then')) {
+    if (is_object($value) && method_exists($value, 'then')) {
         $wfn = method_exists($value, 'wait') ? [$value, 'wait'] : null;
         $cfn = method_exists($value, 'cancel') ? [$value, 'cancel'] : null;
         $promise = new Promise($wfn, $cfn);