使用Heroku和AFNetworking时，PHP缓存无法正常工作

Question

我使用PHP构建了一些简单的GET webservice，返回一些JSON。我已在我的本地测试和缓存工作完全正常。但是当我部署到Heroku时，缓存简单不起作用。

我做了一些测试，服务器返回完全正常的所有缓存标头：

Heroku 标题回复来自AFNetworking：

"Cache-Control" = "public, max-age=86400";
Connection = "keep-alive";
"Content-Type" = "application/json";
Date = "Sat, 20 Jun 2015 05:10:20 GMT";
Server = "Apache/2.4.10 (Unix)";
"Transfer-Encoding" = Identity;
Via = "1.1 vegur";
"X-Powered-By" = "PHP/5.6.10";

来自AFNetworking的

本地服务器标头：

"Cache-Control" = "public, max-age=86400";
Connection = "Keep-Alive";
"Content-Length" = 1711;
"Content-Type" = "application/json";
Date = "Sat, 20 Jun 2015 05:11:39 GMT";
"Keep-Alive" = "timeout=5, max=98";
Server = "Apache/2.4.10 (Unix) OpenSSL/1.0.1j PHP/5.6.3 mod_perl/2.0.8-dev Perl/v5.16.3";
"X-Powered-By" = "PHP/5.6.3";

此外，NSCachedURLResponse始终从我的Heroku网址返回nill。

有没有人对此有任何想法？

顺便说一句：使用iOS 8.3 SDK。