Description:
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http://www.php.net/manual/en/apc.configuration.php#ini.apc.rfc1867

The documentation should be updated to mention that $info['rate'] is only available when the upload of all files are completed.

If a file is uploading and you are checking the status, the upload speed/rate needs to be computed manually.

I thought I had an old or buggy version of apc but it's the current behavior and makes sense:
http://svn.php.net/repository/pecl/apc/trunk/apc_rfc1867.c


Test script:
---------------
// Exampe to calculate the rate as the file is uploading
$info = apc_fetch($key);

if( !isset($info['rate']) ) {
 $ms = (microtime(true) - (float)$info['start_time']);
 if($ms > 0)
  $info['rate'] = $info['current'] / $ms;
}