使用magento安全网址进行操作时，表单提交无效

I have a from that when submit runs a little php to export data to a csv. The php looks like :

$out = '';
if (isset($_POST['csv_hdr'])) {
$out .= $_POST['csv_hdr'];
$out .= "
";
}

if (isset($_POST['csv_text'])) {
$out .= $_POST['csv_text'];
}

$filename = "z_".date("Y-n-d",time());
header("Content-type: application/vnd.ms-excel");
header("Content-disposition: csv" . date("Y-n-d") . ".csv");
header("Content-disposition: filename=".$filename.".csv");
print $out;
exit;

This works fine if I do a normal path to the php file like :

<form name="export"  action="http://website.com/getcsv.php"  method="post"> 

I am trying to move this php function into a controller now and call it that way. I am working on a magento admin module so I have to pass the url with the security key. So I move that function into an action in the controller :

public function getcsvAction(){
    $out = '';
    ...
}

Then I am able to get the url with something like :

<?php echo Mage::helper("adminhtml")->getUrl("module/index/getcsv/");?>

This gives me a link with the key like :

http://website.com/module/index/getcsv/key/7431c859914c40d3f66dfcd1530813b3/

If I paste that link into the browser it executes the php fine. However when I replace it in my form action it no longer works and just does a redirect to the dashboard. I can not see any errors output and I am not sure what is happening. Any ideas on how to get this POST to work using a secure path as the action?

I found it thanks to this post.

I needed to add this to the form :

<input type="hidden" name="form_key" value="<? echo $this->getFormKey(); ?>" /> 

Your URL is missing the adminhtml area. Try this:

Mage::helper("adminhtml")->getUrl("*/module/index/getcsv/");