如何清除iFrame的缓存？

我有一个网页，在其中，我试图刷新一个iframe。我正在尝试使用类似于输入/>按钮和javascript之类的东西来实现它，在不清除缓存的情况下，我似乎无法让iframe重新加载，只有让PHP清除缓存才可以。

更新：

下面是内联的工作实现。

    <input type="button"  onClick="javascript: var iFrame = document.getElementById('compilePreview'); iFrame.src = '<? echo ($myFile); ?>?random=' + (new Date()).getTime() + Math.floor(Math.random() * 1000000);" value="Reload Preview" />
    <iframe id="compilePreview" src="<? echo ($myFile); ?>" width="940"></iframe>

而更大的负载很快就会随之而来，按钮的作用就不大了。

    <script>
    window.onload=refreshIframe;
    function refreshIframe(){
    var iFrame = document.getElementById('compilePreview');
    iFrame.src = '<? echo ($myFile); ?>?random=' + (new Date()).getTime() + Math.floor(Math.random() * 1000000);
    }
    </script>

The first choice is probably to control browser caching for the iframe page from your web server either with HTTP headers or with <meta> tags (see reference).

<meta HTTP-EQUIV="CACHE-CONTROL" CONTENT="NO-CACHE">
<meta HTTP-EQUIV="PRAGMA" CONTENT="NO-CACHE">

If you can't change those, then you can set a .src in the iframe that has a different query parameter each time to go around caching.

For example:

iframeObj.src = "http://www.example.com/page/myframe.html?random=" + (new Date()).getTime() + Math.floor(Math.random() * 1000000);

This is something you should do on the server side, controlled via HTTP headers like so:

<?php
header("Cache-Control: no-cache, must-revalidate");
header("Expires: Sun, 29 Jul 2012 00:00:00 GMT"); // some day in the past

You could do something like

<iframe src="<?php echo $url.'#nocache'.time(); ?>">
#document</iframe>

Which would allow for GET parameters in the URL without also having to worry about whether to use ? or & for your random.