Fix a typo. added jsonbuilder test

dbObject.php

@@ -186,7 +186,7 @@ class dbObject {
      */
     private function JsonBuilder () {
         $this->returnType = 'Json';
-        return $return;
+        return $this;
     }
 
     /**

tests/dbObjectTests.php

@@ -274,5 +274,12 @@ if (!is_array ($p->join('user')->orderBy('`products`.id', 'desc')->get(2)))
 if (!is_array ($p->orderBy('`products`.id', 'desc')->join('user')->get(2)))
     echo "wrong return type2";
 
+
+$json = user::jsonBuilder()->get(null, "id, login");
+if ($json != '[{"id":1,"login":"user1"},{"id":2,"login":"user2"},{"id":3,"login":"user3"},{"id":4,"login":"testuser"}]') {
+    echo "jsonbuilder fail";
+    exit;
+}
+
 echo "All done";
 ?>