PHP Upload Progress Session
===

I am trying to create an upload progress bar with PHP.
I saw the new feature of PHP 5.4: <a href="http://www.php.net/manual/en/session.upload-progress.php">upload progress session</a>.

This is my HTML code:

>> &lt;form id="upload" action="ajax/progress.php" method="POST" enctype="multipart/form-data"&gt;

>>&lt;input type="hidden" name="&lt;?php echo ini_get("session.upload_progress.name"); ?&gt;" value="dupload" /&gt;

>> &lt;input id="file1" type="file" name="file1" /&gt;

>> &lt;input class="btn primary" type="submit" value="Upload" />&lt;/form&gt;


And this is progress.php:
>> &lt;?php

>> session_start();

>> $key = ini_get("session.upload_progress.prefix") . 'dupload';

>> if (!empty($_SESSION[$key])) {

>>     $current = $_SESSION[$key]["bytes_processed"];
    $total = $_SESSION[$key]["content_length"];
    echo $current < $total ? ceil($current / $total * 100) : 100;
}
else {
>> 
    var_dump($_SESSION);
    var_dump($_FILES);
}

All the ini settings are right. (session is enabled, name and prefix is right)

I am always getting an empty session array. What's wrong?

Thanks!