Permissions on PHP-created file for a FTP account

You don't have to 'do' anything. I only need an answer, a solution for a small problem. If your solution works, the reward is $ 20. First on with the golden solution counts (only one can get the reward). I have a Linux server Centos 6.5 with user root. In the Plesk Control Panel I created a Webspace, a domain and then there is the subscription owner's FTP account. With this FTP account a can get acces to the domain (using any FTP client like WS_FTP (Windows) or Cross FTP (OSX). Through FTP I can read, write and delete files. There is a folder httpdocs/log/ with permissions rwx rwx rwx. Using FTP I can upload any file to this folder and it will get permissions rw- r-- r-- User = usr_ecampus and Group = psacln. Of course I also can read and delete this file with the FTP account. The same goes for every other additional FTP account I create through Plesk Panel. Now I create a file through PHP in the very same folder - method fopen($file , 'a'). And the same goes for every (log)file produced by Prestashop. Again this new created file will get permissions rw- r-- r-- User = usr_ecampus and Group = psacln. So, owner and permissions look exactly the same. However, this PHP-created file is not visible for the FTP account. It cannot be overwritten by the FTP account. It is possible to see the file in Plek Panel and it is also possible to edit the file (Edit in text editor) through Plesk. After saving the file, the file is also visible for the FTP account. Permissions remain the same rw- r-- r-- User remains the same = usr_ecampus and Group remains the same = psacln. That's my problem and question. It seems that permissions and owner are not the solution (since they remain the same). What is going on and how can I create a file using PHP which will be visible and accessible for this FTP account? Again: the first one giving me the (working) solution for this I will pay $ 20. Thanks in advance.