Added \JsonSerializable interface to Response->json (issue: #284).

src/Pecee/Http/Response.php

@@ -69,13 +69,19 @@ class Response {
     }
 
     /**
-     * Json encode array
-     * @param array $value
+     * Json encode
+     * @param array|\JsonSerializable $value
+     * @throws \InvalidArgumentException;
      */
-    public function json(array $value) {
+    public function json($value) {
+
+        if(($value instanceof \JsonSerializable) === false && is_array($value) === false) {
+            throw new \InvalidArgumentException('Invalid type for parameter "value". Must be of type array or object implementing the \JsonSerializable interface.');
+        }
+
         $this->header('Content-type: application/json');
         echo json_encode($value);
-        die();
+        exit(0);
     }
 
     /**