I am able to upload a 28 meg file, yet php.ini limits posts to 10 megs. What is up with that?

To guard against users uploading huge files, I've got this in my php.ini file:

; Maximum size of POST data that PHP will accept.
post_max_size = 10M


On a server running Ubuntu Linux. The PHP version:

root@ldc310:/etc/php5/cli# php -v
PHP 5.1.6 (cli) (built: Nov 28 2007 22:52:49)

I just uploaded a 28 meg file to the server. I have a PHP script that automatically resizes the images to less than a meg. However, I was (hoping) assuming that the upload should have failed, before the PHP script ever had the chance to resize the file. How do I limit how much our users can upload? I really don't want the users to have the power to upload 30 or 40 or 50 meg files.

The server does have Plesk installed, which I know, in times past, has found ways to undermine the settings in php.ini. For instance, for open_basedir, the value that gets written in the httpd.conf file, in each vhost directory, takes precedence over whatever I put in php.ini. But I've never seen Plesk undermine the importance of the post_max_size setting, nor can I imagine where Plesk might store such a conf setting if it did.

Any thoughts on what might be wrong? Are there other places some configuration data might be taking precedent?
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