Allow serializing stdClass objects

Fixes sebastianbergmann#5

Author: mrclay

src/Snapshot.php

@@ -406,6 +406,10 @@ private function canBeSerialized($variable)
             return !is_resource($variable);
         }
 
+        if ($variable instanceof \stdClass) {
+            return true;
+        }
+
         $class = new ReflectionClass($variable);
 
         do {

tests/SnapshotTest.php

@@ -31,6 +31,7 @@ public function testStaticAttributes()
         $expected = array('SebastianBergmann\GlobalState\TestFixture\SnapshotClass' => array(
             'string' => 'snapshot',
             'arrayObject' => new ArrayObject(array(1, 2, 3)),
+            'stdClass' => new \stdClass(),
         ));
 
         $this->assertEquals($expected, $snapshot->staticAttributes());

tests/_fixture/SnapshotClass.php

@@ -23,6 +23,7 @@ class SnapshotClass
     private static $arrayObject;
     private static $snapshotDomDocument;
     private static $resource;
+    private static $stdClass;
 
     public static function init()
     {
@@ -31,5 +32,6 @@ public static function init()
         self::$arrayObject = new ArrayObject(array(1, 2, 3));
         self::$snapshotDomDocument = new SnapshotDomDocument();
         self::$resource = fopen('php://memory', 'r');
+        self::$stdClass = new \stdClass();
     }
 }