These two settings need to be the same and should be 16-18mb in all versions of PHP. I had problems importing a 12mb xml file in PHP7.0 with my Joomla 3.8.3 site and it kept failing because of the post_max_filesize being 8mb. Finally, I found that PHP5.4 had the setting at 18MB and the import worked. I would much rather use 7.0 so it would be most helpful if the admins could check all PHP versions and get these settings to match AND to be of a suffice size to accommodate common files sizes in use today. Thanks!!