PHP 是否可以设置为从不缓存响应，并始终向页面发送新内容？

发布于 2024-11-17 19:57:29 字数 214 浏览 4 评论 0原文

我有一个提取 XML 新闻提要的网页，但我不希望页面缓存它，以便显示的 XML 提要是最新的。

我已经尝试过此操作，因此缓存每 1800 秒重置一次：

$header[] = "Cache-Control: max-age=1800";

似乎不起作用。

那么我可以尝试如何让网页自动刷新 PHP 中的 XML 呢？

原文

I have a webpage which pulls in an XML news feed and I don't want the page to cache it so that the XML feed displayed is most recent.

I tried this already so the cache is reset every 1800 seconds:

$header[] = "Cache-Control: max-age=1800";

Didn't seem to work.

So what could I try to make the webpage auto refresh the XML in the PHP?

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睡美人的小仙女 2024-11-24 19:57:30

试试这个，

<?php
header("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1
header("Expires: Sat, 26 Jul 1997 05:00:00 GMT"); // Date in the past
?>

这将阻止页面缓存在用户的计算机上。

Try this,

<?php
header("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1
header("Expires: Sat, 26 Jul 1997 05:00:00 GMT"); // Date in the past
?>

This will prevent the page from being cached on a user's machine.

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别把无礼当个性 2024-11-24 19:57:30

通常在 php 中我设置这些标头以避免缓存：

header( 'Cache-control: no-cache' );
header( 'Cache-control: no-store' , false );
header( 'Pragma: no-cache' );
header( 'Expires: 0' );

但不清楚你在做什么。您是否正在调用输出 xml 的 php 页面？

在客户端，我通常为每个请求添加一个参数（&time=actualtimestamp），以便浏览器不会缓存它。

Usually in php I set these headers to avoid caching:

header( 'Cache-control: no-cache' );
header( 'Cache-control: no-store' , false );
header( 'Pragma: no-cache' );
header( 'Expires: 0' );

But it is not clear what are you doing. Are you calling a php page that outputs xml?

Client-side, I usally add a parameter (&time=actualtimestamp) to every request so that the browser doesn't cache it.

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心意如水 2024-11-24 19:57:30

如果可以，请执行 post 请求来获取 XML。 Post 请求不可缓存。

如果您无法执行发布请求，请在请求的查询信息部分添加一些唯一的内容
URI，就像当前时间：

old: http://exmaple.com/data.xml
new: http://exmaple.com/data.xml?878621387
                                  ^ random number

我首先读错了你的问题，并担心你想阻止你的响应被缓存。也许它仍然有用，所以我把它留在这里：

在流行的应用程序中，经常存在设置一堆标头以防止缓存的函数。这是来自 WordPress 代码库的示例：

  function nocache_headers() {
      @ header('Expires: Wed, 11 Jan 1984 05:00:00 GMT');
      @ header('Last-Modified: ' . gmdate('D, d M Y H:i:s') . ' GMT');
      @ header('Cache-Control: no-cache, must-revalidate, max-age=0');
      @ header('Pragma: no-cache');
  }

它设置 将 标头过期到过去的日期。因此，在交付时，文档已经过期或在缓存方面已过时。这些文档不应该通过缓存传递。

然后是 Last-Modified 标题设置为当前时间。

然后 Cache-Control 标头设置为缓存不应缓存响应，必须重新验证，并应保留最大年龄为 0。这听起来可能有点精神分裂（就好像没有缓存，不可能有年龄），但这只是用数据淹没代理和用户代理以使它们停止。

最后是 Pragma 标头设置为 no-cache 以防止 HTTP/1.0 兼容代理和用户代理的缓存（HTTP/1.1 客户端通常使用缓存控制）。

所有这些标头在超文本传输协议 -- HTTP/1.1 RFC 2616 中有详细解释菲尔丁等人。如果您渴望查看可用的选项，请参阅第 14 节标题字段定义。

If you can, do a post request to obtain the XML. Post requests are not cache-able.

If you can not do a post request, add something unique to the query-info part the request
URI, like the current time:

old: http://exmaple.com/data.xml
new: http://exmaple.com/data.xml?878621387
                                  ^ random number

I first read your question wrong and was concerned about that you want to prevent that a response of yours is being cached. Maybe it's still of use, so I leave it here:

In popular apps there often exists functions that set a bunch of headers to prevent caching. This is an example from the wordpress codebase:

  function nocache_headers() {
      @ header('Expires: Wed, 11 Jan 1984 05:00:00 GMT');
      @ header('Last-Modified: ' . gmdate('D, d M Y H:i:s') . ' GMT');
      @ header('Cache-Control: no-cache, must-revalidate, max-age=0');
      @ header('Pragma: no-cache');
  }

It set the Expires header to a date back in the past. So while being delivered, the document already expired or in caching terms is stale. Those documents should not be delivered by caches.

Then the Last-Modified header is set to the current time.

Then the Cache-Control header is set to signal that caches should not cache the response, must revalidate and should keep copies for a maximum age of 0. This sounds a bit schizophrenic maybe (as if not cached, there can't be an age), but that's just to flood proxies and user-agents with data to make them stop.

Finally the Pragma header is set to no-cache to prevent caching as well for HTTP/1.0 compatible proxies and user-agents (HTTP/1.1 clients normally make use of Cache-Control).

All these headers are explained in detail in the Hypertext Transfer Protocol -- HTTP/1.1 RFC 2616 Fielding, et al. Section 14 Header Field Definitions if you're eager to checkout the options available.

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