Question: I'm running into a strange issue when uploading large files via PHP (through Drupal, though that's not the issue).

Basically, my file uploads fail due to post\_max\_size limits being reached, even though the local directive is set to 96M, and the file is 25M. 

I've ensured everything else is correct, including `max_input_time`, `max_upload_filesize`, and the IIS FastCGI idle time. All these are plenty large and not the issue.

I am overriding the `post_max_size` directive through Plesk, which (I believe) stores the change in a registry value. Running phpinfo() on the domain shows the correct local and master values for all directives...96M local, 12M master.

The very strange thing is that when I change the master `post_max_size` in php.ini from 12M to 96M (and ensure the change has taken effect), **it works normally!** Changing the master value back to 12M (and keeping a local value of 96M) immediately causes uploads to fail again.

Is this a bug in PHP, or am I doing it wrong?

Answer: 
Check PHP's post\_max\_size and upload\_max\_filesize in php.ini and for any overrides (local php.ini or .htaccess for example)

EDIT: it should be noted that phpinfo() cannot be relied upon for determining if any override will be available during the request (aka when file uploads happen) since it will be processed during the response.
I had similar issues in Plesk. Have you edited any of the templates in Plesk? I know when it runs its cron jobs you can lose certain config edits if you didn't do them via Plesk.

But what about your .htaccess file? You can also set these limits there and that, based on your Plesk config, may the better place to make these changes.